Very few people are happy that Casey Kotchman is the Mariners' First Basemen.  The defense is nice, but hardly anyone sees his upside, at 27, as more than a .790ish OPS, and a lot of people not even that.  We all know the argument by rote:  Kotchman's mediocre power is supressed by a ludicrous percentage of groundballs, which is especially bad since he's too slow to beat out a decent percentage of infield hits.  The consistant talk of Wakamatsu leaning toward batting Kotchman third is no doubt blood curdling to most fans.  I, however, think it's a great idea, and there's a lot more potential in Casey Kotchman's bat.

The first reason to expect a big improvement from Kotchman are the homeparks penalizing right field homeruns.  Angel Stadium wasn't very bad (but below average), but Turner Field was worse, and Fenway is awful to Right.  By contrast, Safeco is among the league's easiest parks to homer to right, which makes Casey Kotchman a near perfect fit.  Kotchman hits nearly 47% of his balls in play to right, Ken Griffey pulls 49% and gets the shift (these numbers are 30.5% and 34% per Baseball-Reference).  

The suppression of Kotchman's earlier home stadiums shows up in his home/away splits, since 2007, he's hit 10 Homers at home and 22 on the road, since 2008 it's 4 at home to 17 on the road.  

Moving on to his groundball tendencies, whether you believe he's exeptionally slow or not (he's scouted as having good speed for a firstbaseman, and hits into double plays at a league average rate, AL players GIDP on 6.72% of ground balls, Kotchman is at 6.73%), he is certainly among the slowest players to average over 50% groundballs in play, which is the major part of his game holding him back.  There is once again a solid ray of hope though, since 2007, when he plays on the road, his balls in play divide up thusly:  18.1% LD/48.2% GB/33.7% FB/10.2% HR/FB, each rate better than his career averages (and significantly better than what he ran at home obviously).  Why the Jekyll & Hyde act?  I would guess that playing games, and maybe even in batting practice, Kotchman realizes that his flyballs tend to fall short more often than at other stadiums, and adjusts his swing.  In Safeco, he won't feel like he has to make any sort of adjustment.

Another question has been, who can you compare him to so that you might guess what he'll do at age 27 and beyond.  Baseball-Reference isn't much help, most of the comps it displays didn't hit a lot of groundballs (or there isn't any data one way or the other), or they didn't have good plate discipline, or they were part time players in their age 27-30 seasons.  So I've drifted through Baseball-Reference looking for players that matched up physically, and in balls in play tendency, and in plate patience.  I found two.

The first is Sean Casey, who is a good representation of what I believe Kotchman will look like if he gets his overall groundballs down to his road rates.  When Casey was healthy, he generally put up good, if inconsistant, numbers, ranging between a .750 and .900 OPS until he flamed out at 33.  The major thing he did better than Kotchman was line drives, where he stood at 25%, leading to a .320 career BABiP) compared to Kotchman's 17%, but then Kotchman strikes out less and hits a higher percentage of his balls in air for home runs despite hitting in unfriendly parks.

The second is none other than Joe Mauer.  In terms of groundball to flyball ratio, and home run ratio (for their careers, obviously Mauer ran away with it last season), the two are practically identical.  Here, the major difference (in terms of batted balls that is, Mauer walks significantly more often) is once again BABiP, where Mauer leads Kotchman by 70 points, but unlike with Sean Casey, the gap can't be easily attributed to line drive gap as Mauer at 20% is better, but not 70 points of BABiP better.  Mauer might once have been faster than Kotchman, but after so many years of catching he's probably slower if anything now and last year he put up the best BABiP of his career.  Artificial turf...sees him produce a nearly identical BABiP to grass.  Maybe Kotchman has been unlucky this whole time, he's running a .433 BABiP in spring training so far and if he carries that into the season, he's golden.

The point is that both those players have put up several .850+ OPS while looking very similar to Casey Kotchman in most of their stats except for BABiP.  The line drives are better for both players, but Kotchman has generally had more success with turning balls in air into home runs, plus his BABiP has been unlucky the last two years, at least after he was traded each year (.279 to .252 in '08, .292 to .272 in '09).

Among things that Kotchman does well now, in opportunities for productive outs, Kotchman succeeds in advancing the runner 45% of the time, compared to major league average of 32% (this stat doesn't inlude hits or walks in opportunities), and more interestingly, scores 17% of the baserunners he inherits compared to a major league average of 14%.  Other things he has going for him:  He's coming to an organization that is emphasizing plate patience, which could lead to a higher walk rate for him, Dr. Elliot may coax more line drives into his swing, and batting third, you can expect his BABiP to improve, as the first basemen covering the bag opens the right side of the infield to him (of course there is the danger of double plays, but with the hitters being the fleet Figgins and Ichiro and Kotchman's 90% contact rate, there will be a lot of hit and runs).

Finally, what do I think you can expect from him this year?  If only some of these things break right for him (improved BABiP, easier home park) I think an .800-.850 OPS is well within his reach.  But if most of this stuff goes the way I think it will (Better batted ball profile, improved line drive rate, better patience) he could easily top a .900 OPS in the same way that Mauer or Casey have before.