Is that you keep harping on Adrian Beltre's 2009, a season that he started while recovering from shoulder surgery to remove a bone spur, a surgery that missed the bone spur (or saw it regrow - they do that) and had to have a second surgery on his shoulder in late June.  Then, in August, he ruptured a testicle.  With all that he still managed 2.5 WAR in 111 games.  I don't think it was so much Safeco that conquered Beltre in 2009, I think it was injury.

Adriand Beltre wasn't taken down a peg or 2 in Safeco, of course he was.  Virtually any right handed hitter would be.  My argument is that Safeco didn't crush him, and demoralize him until he was a shell of a player. 
You talk about his Slugging Percentage slipping.  From 2007 to 2008 his ISO went down by .016, it's not a huge drop, and his BABiP that year was almost .020 points lower.  In there, I would guess he lost a few doubles that led to slightly diminished power numbers, I've already expressed my thoughts on 2009 being very explainable. 
You talk about a massive uptick in WAR before and after his time with the Mariners, yep, he's a star outside of Safeco, but while he was a Mariner he did put up a 4.9 Win season, followed by a fluky 3 Win season that was his best offensive season with the Mariners (and would have been better had he gone on the DL sooner in September that year) but was the only season in the last 9 where he actually put up negative numbers as a fielder.  Had he put up his normal +10 that year, it would have been another mid 4 win season for him.
But yes, of course I believe Adrian was held down by Safeco, as well as by playing for a consinstently cellar dwelling team.  And, being the ridiculous competitor I've read he is, probably pressed to beat the stadium, and because he was too often counted on to be the best hitter on the team.  He probably lost an offensive "Win" per season to Safeco, and what would probably be a lock for a Hall Of Fame career otherwise will now depend on him continuing to put up numbers like he did last year well into his 30s.
However, I'm going to go with the mindset that players like Adrian Beltre and Franklin Gutierrez are not so easily beaten into simply allowing something so simple as a home park to beat them.  Adrian Beltre was constantly regailed as a failure in LA until his break out 2004 and has bone spurs that constantly grow and derail his career (You probably google news stories about it from 2004, 2007,8, and 9).  I've read several times that his workout regimin is second only to Ichiro's in it's thoroughness. 
If Adrian Beltre gets beaten by a stadium because it holds him to 25 home runs a year, then how do players like David Eckstein not simply become quivering masses?  One of the favorite players to be talked about here, Mike Wilson, has been banging his head against the minor league wall for 9 seasons now, and every year his chances of ever making a major league roster as anything more than a "Thank you for being organizational filler" dwindle, but he, and a thousand other 30 year old minor leaguers go out and put up impressive numbers any way.
So why would your home park make you start phoning in your performance in one of the most competitive jobs on the planet.  Richie Sexson got beat, by the park and by home town fans continously booing him at every plate appearance, and then he was done at 32, but he was a guy that only ever really did one thing, hit balls out of the park - he didn't field, or hit for average, or steal bases ever.  If hitting home runs is your only skill as a hitter, then yes, Safeco will kill you, but Beltre and Gutierrez don't rely on home runs for their offensive game, those are nice, but they can still be productive without them.

Beltre was clearly a really bad fit for the park, but I think its a bit overblown. I think Beltre was probably on steroids in '04 and '10 was a legitimately great season boosted by luck/park.
'10 was significanly higher than his career BABIP and power slightly inflated at Fenway (but not rediculously so).
Beltre hit 25 HRs three seasons in a row in Safeco and hit 28 in Fenway last year. The doubles were the biggest help. Those long flyballs are outs in Safeco so part of the BABIP spike is probably legitimate.
Beltre is likely a neutral park low 800s OPS guy that Safeco turned into a 790 OPS type. Hes in a hitter's park with Texas now, but I'd bet on an OPS around 82-830 ish.

Sorry, Doc ... on Beltre, I'm afraid you've gone down the "find data to prove my thesis" rabbit hole, instead of looking at ALL the data.
When in doubt about the impact of a HOME field - what is the obvious solution.  Look ONLY at "AWAY" numbers.
Here are the ROAD numbers for Beltre in 2009 and 2010:
2009:  .279/.324/.393 (.717)
2010: .327/.370/.583 (.953)
Note:  In 2009, Beltre hit 71 points worse at home.  In 2010, Beltre hit 72 points worse *AT HOME*.
While everyone is sitting back ASSUMING that Beltre got some massive boost from Fenway, the truth is ... he hit exactly as bad at home (in relation to road) playing in Boston in 2010 as he did playing in Seattle in 2009.  If injury was NOT the issue with Beltre in 2009, then one would expect his ROAD batting line to at least be on the same continent.  Heck, it's not even in the same hemisphere.
It's also disappointing to see you chop off his slugging progression to only include the years that support your conclusion, while leaving out the .413 and .462 slugging from years one and two.  Prior to 2009, his career slugging was .459.  That makes the 2009 season a massive outlier, and the year 2,3,4 performance looks REMARKABLY stable. 
For '06 to '08, you've got a .792 -- .802 -- .784 sequence of OPS figures.  That's mind-boggling consistent.  That's 450 games of stable, reliable, almost robotic performance, where his 2008 numbers are actually the second BEST season he had in Seattle, (by OPS+), which adjusts for offense dropping league-wide.
Yet, your perception is that after 450 games of rock-steady production, in 2009, Beltre got depressed about the park?!?
The problem with the "Blame Safeco" perception is that it obliterates the club and players EVER taking responsibility for their performance.  Lopez had a lousy 2010, so the mass opinion is "the PARK killed him". 
People in parks in other LEAGUES have career bad years all the time.  It happens.  And yes, depression can play a role, (I'd be depressed too, having to play for an organization as inept at player development as Seattle).  But, JUST LIKE GRIFFEY, the "emotional" reset of moving almost certainly played a role in Beltre having another career year.  He's an .837 career ROAD hitter, who had a .953 ROAD OPS in 2010. 
But, if everyone, (club and fans), continues to blame the park for every right-hand hitter having a poor season, then the club will never fix the actual problem, and the fans will never actually get to see a bounce-back year. 
Me?  I think the park had ZERO to do with Gutz bad 2010 -- and the clubhouse implosion and  year-killing Nap-Gate episodes eventually caused everyone except Ichiro to swirl down the porceline.
 

MOST hitters - whether they move or not, tend to bounce back after a horrid season, unless they have aged out.
Honestly - here's my question.  Other than Richie Sexson, (who did NOT go on to hit decently elsewhere) - how many right-hand hitters have seen their offense plunge 'significantly' - (the safeco killer effect) for MORE than a single season - say 550 ABs?
What is the actual sample set of players ALLOWED to return after a well-below-standard season?
No one is arguing that Safeco isn't a pitcher's park.  Yes, the Safe will cost a player ... what, 50 points of OPS *AT HOME*.  That translates to a 25 point reduction in OPS, with 1/2 the games being away from the Safe. 
Cameron played 4 full seasons in the Safe - with a career year in his 2nd.  He showed NO long-term detrimental effect from playing in Safeco, (and the highest hitter suppression seasons were actually years 1-3).  His final OPS+ was 108, his first with the Mets 104.  He had one more "career year" at age 33 - which was still two points of OPS+ under his career year in Seattle.
Yes, Cirillo was awful in Seattle.  But, his 33 games in 2004 with San Diego, he had an OPS two points WORSE than his final season in Seattle.  Sample size makes the analysis bogus - but Cirillo did not "instantly" start hitting after leaving Seattle.  (And, of course, coming from Coors to Safeco is about the most extreme example of park sloth I can fathom).  Even at that, Cirillo only got 700 ABs before he was gone.
Heck, in Beltre's FIRST season, he was dreadful.  He then got BETTER after spending a year in hitting hell. 
Do, I expect Lopez to have a great season?  In COORS?!?  Of course.  But, I'd expect ANY hitter, (right, left or switch), to hit better in Coors.  I also expect any hitter under the age of about 34 to bounce back after a bad season.  I dominated an expert fantasy league by stealing the bounce-back guys in later rounds. 
You don't have to leave Boston to see an example -- Mike Lowell, the guy Beltre replaced, gets added as a salary-dump throw-in after posting a 77 OPS+ at age 31.  Everyone and their brother was screaming 'pharmacy' and nobody wanted to touch him.  He posts .798+ OPS figures the next four seasons.  And at age 36, he falls off the table.  NOT a smart bet for a bounce-back this time.
The problem is you can NEVER know what would've happened if a player had stayed (or moved). 
However, I completely understand why any player who REALLY sucked while playing in Seattle would say very publically that "the park did it".  It's in their best interest to do so - and human nature to place blame elsewhere when we can.  I expect players to blame parks the way I expect politicians to blame the opposition party.  That's just the way it is.
Did Safeco kill Johjima?  He hit .609 at age 32 - a 63 OPS+ after two years at 100.  He bounced to .702 (87) in his final 250 ABs.  Does that prove your point or mine, Doc?  He lost 40 points off his OPS+ and then gained 25 back, in part time play, while injured, while at the age that most catchers tend to begin aging out.
In many ways, Lopez line matches up with Johjima's.  Except Lopez was only 26 this year.  NOT aging out.  If he remained - and was healthy - I believe a 100 OPS+ could easily be the result.  But, there's no way to know.  I would suspect that the tendency for horrid year transfers to do a bit better than stay-put bounce-back guys.  The change of scenery can help, of course.  But, I would suspect if someone did a study of 50 guys with career disaster years (before age is a major issue), you'd see fairly similar results, regardless of which teams were involved. 

Other than Richie Sexson, (who did NOT go on to hit decently elsewhere) - how many right-hand hitters have seen their offense plunge 'significantly' - (the safeco killer effect) for MORE than a single season - say 550 ABs?
What is the actual sample set of players ALLOWED to return after a well-below-standard season?
Most of the batters were not allowed to come back, you're right Sandy.  We weren't able to tell over multiple seasons if it was the park or just the move to a new league/park or just bad luck that did it.  But watching Cirillo or Beltre in the batter's box was a totally different experience from their previous locations.  Demoralized.  Beltre came back because he had a big contract, and is the biggest example of the Safeco Phenomenon of watching fly balls go to die in the outfield messing with an approach.  His recovery was everything I expected it to be.
Cirillo came from Colorado and TANKED here.  The park decimated him.  He was a good player before Colorado, though, and once returned to Milwaukee, he was good again.  
29 in MIL - .862 OPS
31 in COL - .838 OPS
32 & 33 in SEA - .629 and .555 OPS
35 & 36 in MIL (part-time) - .800 and .774 OPS
Comfort level was big for Cirillo.  He was never comfortable here - didn't get along with Lou and was way too self-critical to survive the park - and it showed.  Those were painful, painful ABs to watch.
Spiezio was good again: .787 OPS in Anaheim, then .595 (!!) here, then .807 after he went to STL.  Yes, he was a switch-hitter, but the park mauled him.  He was a deer in the headlights up there.
Aurilia was good again. .775 in SF, .641 here and so tormented we traded his ass immediately, then back to .782 and .867 in a small park in Cincinnati.  Part of that was defense - he'd built a career as a marginal SS out of knowing every hitter and every pitcher, and the move to the AL destroyed his defensive knowlege and didn't allow him to position correctly, and that probably messed with him at the plate as well, but the park DID NOT help.
It happens, Sandy.  I hold the middle view of Guti, but we've been watching RH batters or borderline hitters have their livers devoured at the plate in Safeco Field for years now.
Guti in Cincinnati is a monster.  Monster.  I can understand Doc's 2000-pounds-of-ants view of Franklin's future here.  I really can.  I think that his tanking last year was a combo platter, though, of the pressure of the field added to the pressure of NEEDING to hit those homeruns to drive the offense because no one else could.  With the batters who have died here it wasn't necessarily just the park either, but it adds weight to their other concerns.  It IS a factor.
If we can get him just to hit like he did in year one, he'll be fine.  The park works great for RH batters who can go the other way and take the double.  If you live and die by hitting 350 foot HRs, this is not your park.
Franklin doesn't play like he's scared of the park, but even if he's okay hitting there you can't MAKE Safeco cough up RH home-runs.  Sometimes they'll be there to take, but mostly you need to take what it gives and don't force it.
If Gutierrez can stop trying to force the issue I think he can get back to 2009 and we'll all be happy to have him.
If the park's in his head now and he's trying to muscle up to drive it out, forget it.  The ants will claim victory.
So let's hope Doc's wrong. :)
~G

I think I finally understand.
Spezio and Aurillia come to Seattle after the 93-win 2003 season, replacing Carlos Guillen and Cirillo (and McLemore, who also collapsed in 2003). 
Aurillia has a terrible 261 AL ABs and is traded back to the NL, where he hit again.  It wasn't changing leagues or coming to a 93 win team that collapsed to only win 63 ... it was the park that did him in ... the park where he had an OPS 8 points *HIGHER* than his road OPS.  (.671 to .663). 
Spezio, managed 415 PAs in 2004 and another 51 in 2005 before departing.  In 2004, he hit great for two months, then tanked the rest of the season, (a pattern eerily similar to Guti).  But, looking further, Sepzio *ALSO* had a higher OPS (only 5 points) .637 to .632 at HOME than he did on the road.
I don't know.  Maybe my logic is flawed ... but, I just have this inexplicable belief that if a PARK is killing a hitter, then one would expect that hitter to hit worse in that PARK.
In truth, once upon a time, I believed in the Safeco myth -- and attributed Sexson's destruction to the evils of the Safe.  But, upon further reflection, the problem was NEVER Safeco.  The problem is in the basic dangers of the baseball mercenary.  When you rent a player, who has ZERO organizational investment, then you set yourself up for players to blame the org (or park) for their personal failures.  Cirillo, Spezio, Aurillia, even Sexson and Beltre all have one thing in common other than being right-handed.  They were mercenaries. 
Gutz, on the other hand, was given his FIRST full-time chance at MLB success with Seattle. 
Funny thing that Edgar and Boone and even Cameron never had problems with Safeco.
"Signed as FA".  That seems every bit as common as "right-handed" when Identifying the "safeco killed" guys.  Of course, two of the three you bring up showed up for the 30 win swoon of 2004 ... and Gutz, just like Spezio, got off to a torrid start, and only slumped horribly after the club tanked.  (Then again, Aurillia hit .715 in the 2nd half after hitting .641 in the first half, so go figure).
"How would I know I'm wrong?" the Doc asks.
1) If a player hits BETTER at Safeco then elsewhere, the problem, whatever it may be, is not likely to be Safeco.
2) What's the ratio of players this impacts to those it doesnt?
3) How many PAs for these players are avialable? (what's the sample size being examined?)
Imagine this for a minute.
In 2005, Beltre comes in and hits .716 (93 OPS+).  If he had been IMMEDIATELY traded, and hit .792 (105) at his next stop, would his performance have been 100% attributed to park effect?  I say it would've been.  Because the primary foundation for the Safeco Effect killing hitters is tied up in 3 hitters (Cirillo, Spezio and Aurillia), who lasted 800, 500, and 250 ABs and were gone, (and two of those hitters were here in the midst of the 2004 collapse).
If the park is to blame at all - it is at best, IMO, a mitigating factor.  The real blame is in acquiring players who are such mental weaklings that they crumble and quit in response to the first hardship.  Kotchman was not right-handed.  The park isn't supposed to kill lefties.  But, Kotchman was a guy whose entire profile screams "I'm fine until something doesn't go my way."
It's players with the Emotional IQ of a 2-year-old that crumble in Seattle.  But, with an organization that hasn't produced a decent hitter (outside of Lopez) in a decade, why blame the park.  Kotchman imploded.  Vidro imploded, (another switch hitter).  Wilkerson imploded.  Clement failed miserably.  Reed failed miserably.  (But, somehow, Guillen was completely immune from the effects of Safeco in his one year stay).  Bradley is another switch-hitter who imploded.
As to the "you have to see how these guys looked" argument.  No, I don't.  I've seen PLENTY of completely distraught teams, (I watched the Braves since the 70s, so I saw 2 decades of last place teams).  Guess what.  LOTS of players in lots of parks look utterly hopeless when they're 30 games back. 

I do think mental weakness, emotional insecurity whatever you'd like to call it is a big deal.  Chone Figgins shouldn't have had a huge park effect but tanked in the first three months of a new situation with a lot of other stressers.
But when Beltre got to this park, we were treated to stories about how downtrodden he'd get when he hit a ball on the screws in early April, in the cold damp air, and how he'd start a home run hop only to see it die on the warning track.  We had stories from Cirillo doubting his ability to ever hit again, and watched the arguments between him and Sweet Lou.  Beltre might be insecure and Cirillo was hugely self-critical, but seeing it happen and having newspapermen do interviews where they recount clubhouse stories of what was going on as it was happening don't help us shake the "Safeco murders the confidence of right-handers" mentality.
And it's not just marginal guys.  Alex Rodriguez hit 15 more HR on the road than at home in 2000, and had 84 more points of batting average.  I remember him making "that shoulda been a HR" face several times that year, and he complained about the park.  When one of the greatest RH hitters ever tells you he hates your park, then the park might be an issue and maybe the fans aren't just "making it up."
In the entire history of the park, there haven't been that many right-handers who hit well here.  Edgar did well...and he still lost 100 points off his Kingdome marks.  It was the tail end of his career, so it makes sense, but he wasn't trying to clear fences either.  He took what was given to him. 
Boone was also good here, thanks to steroids and choking up on the bat to quit swinging for the fences with 2 strikes and just trying to put the ball in play. 
Carlos Guillen IIRC was decent here, or at least not huge on the road compared to his Safeco numbers.  But he was a switch-hitter who also blossomed the second he left.  That had a little something to do with us blaming him for Freddy's drinking and screwing up his TB diagnosis, thus nearly killing him.  Can't blame that one on the park, but the fact that he blossomed the second he got out of our organization puts another question mark out there.
There is just a pile of bodies 10 feet high around the Safe of RH hitters.  For every Jose Guillen, who came into the park and survived (dropped 50 OPS points at home, but since it's a pitcher's park that's to be expected, and his HR stayed even) there are two or three that didn't.
The guys building the team are so afraid of RH bats here now that they pissed off the Yankees by not trading for the best RH hitter in the minors with their Cliff Lee chip.  We'll only "risk" a RH bat at a glove position.
I agree with you that being mentally weak is the component that the Park factor exacerbates.  But does the park help cause that weakness in the first place?
Mike Cameron hated Safeco.  HATED it.  He fought through it, but it was winning.  We'd painted the wall, put up trees, made that honeycomb thing out there, all trying to help the batters see the ball.  I don't know if seeing the ball was the problem or not in the beginning, but Cammy crushed the ball on the road, and would wilt visibly at home trying to play the same game.
If a guy is OPSing in the .900s on the road and in the .600s at home, something is wrong.  Safeco started to train him, though, and he started dragging his Safeco averages up a tick...while his road averages dropped.  He stopped swinging for the fences on the road as well.  The park was killing his game (or at least that's how it felt watching him), causing him to hold back on his power for fear it wouldn't be enough.
I think it's watching what happened to Cameron that's causing the Guti questions.  We saw what happened when the park got into his head enough that he had to take away the risk/reward of his away game so as not to be completely inept at home.
Maybe it won't happen to Franklin.  Maybe he can keep it together and keep hitting those power shots over the fence.  So far he seems Guillen-like to me (Carlos or Jose, take your pick).
And I still think he would blossom immediately upon leaving the Mariners, and that you would claim that wasn't related to the park either. 
And maybe it wouldn't be.  But when the franchise is running from RH bats, and the RH bats that have played here, be they Hall of Famers or journeyman, have complained about the park, it might be an issue.  Or at least people that play at the park and employ those players believe it is.
Which makes it hard for us as fans to believe otherwise.
~G

Doc,
I'll jump in here, maybe with the last word.
If you discount Beltre's outlier '04 (that may have been artificially aided, if you as me...either that or Mercury just alligned with Mars).....then his Marnier years (OPS+ right at 100) was not that different from the rest of his previous career.  Pretty dang close, in fact.  Beltre was over 100 0PS+ in 3 of his 5 Mariner years. (and only 2 of 5 in the pre-'04 years).
In many ways his '10 was very similar to his '07 year in Seattle.  28 homers compared to 26.  49 doubles compared to 41. 
Last year, however, he lit it up with a .321 average....45 points better than anything he had as a Mariner.
In '04 he hit .334, BTW.
As a Mariner his BABIP was between .276 and .301.  Last year it was .331 (and .325 in '04)
So, I don't see a player "crushed" emotionally by Safeco.  I see a player who had some very productive years in Seattle...who had a terrible '09, much of that injury related.  I also see a player who seems to have lost some hits in Seattle (BAHIP)...but I don't know how to do a home-away comparison there. 
As it turns out, letting him go was a bad move...driven by expense.  We got a lousy over-paid Figgins, albeit somewhat cheaper, in return.
I suspect that Beltre would have returned to his 100+ OPS+ days if he had stayed in Seattle last year.
I see a guy who had a sore testicle  in '09.  But not a player absolutely suffocating under the weight of Safeco.  Not at all on that point.
moe