So, *HOW* does a Kevin Rivers come from nowhere to lead a low minors league in OPS?

The answer is both simple and complex.  I'll start with a simpler question:

How many baseball coaches across America are "decent"?

I work at the National Center for Health Statistics.  Once upon a time, I was asked by a visitor:  "How many people work here?"  "About half," I quipped.

Well, that is probably a humongously generous estimate of competent baseball coaches.  How is that that Tom's River, New Jersey seems to get a team deep into the Little League World Series repeatedly?  The answer is NOT that there is magic baseball dust in the toxic waste dumps of Eastern New Jersey.  The answer is ... a *GOOD* baseball coach can make a humongous deal in the success of totally raw talent.

COACHING MATTERS in baseball, probably moreso than in any other sport on the planet.  Even if you have a Bonds-esque eye, you could end up being a designated walker if you have a swing that is severely screwed up.  My Little League horrors are 40 years in the past -- but the sum total of the coaching I got in 3 years of bench warming was:  "Choke up on the bat."

Doc and Spec are probably 10 times more qualified to coach baseball than at 3/4 of the high school baseball coaches getting paid to do so, (most of whom were natural athletes, and also likely learned nothing more than "choke up on the bat" along the way).  I'd guess they're 5 times better than 3/4 of the Junior College coaches - and twice as good as the majority of the D-II baseball coaches.

It's an unfortunate reality that if you have the SMARTS to have learned something about the SCIENCE of hitting, you're more likely to be a programmer or contractor or any one of a thousand jobs that pays tons better than baseball coach.  (Let's face it, short of the MLB, few baseball coaches are making enough money for there to BE a great deal of talent in teaching to fill the 10,000+ open positions).

And then there's the "star" problem.  Every team HAS the "naturally gifted athlete".  He's the best in every sport - pitches in baseball - slugs .800 -- is the starting QB.  HE has the perfect swing - but he doesn't KNOW anything about how he got it.  Yet, this is the guy that the most time will be spent on.  HE gets all the "instruction", (a good portion likely detrimental, until he gets significantly higher on the learning totem).

There's a reason that 34th round draft picks ROUTINELY succeed in baseball, and almost never do in any other sport.  It's because the teaching methods in every other sport are about 1000 years ahead of baseball.  Okay -- in the past decade or two, the birth of the instructional video tape has likely improved the baseball landscape dramatically - (upgrading from Baltic to Mediteranean).

The sad truth is that the likely bulk of guys who COULD teach hitting somewhere, are probably do so at the local country club -- because teaching golf swings to executives is WAAAAY more lucrative than teaching hitting to teenagers. 

Of course, some Division I schools have strong reps for churning out MLB players.  Yes, recruiting plays a role - but INSTRUCTION is probably the real key.  You've got 25 kids who are ALL getting their hitting optimized.  Meanwhile, the guy going the JC route is (in most cases) left to his own devices, muddling along on pure ability and instinct - (but not having the over-the-top athleticism that gets you a ride at somewhere meaningful). 

While there ARE minimum physical standards - (bat speed, reaction time) - that are immutable.  If you meet those standards, then the rest of the game gets very cerebral, very quickly.  Guys like Piazza get a shot because a friend of friend wanted to be helpful - and then at some point, they pick up some knowledge they didn't have before, and a door opens.  If they'd have that knowledge back in High School, maybe they would've been the star - and gotten the juicy scholarship. 

Of course, you also have the guys who just can't seem to apply instruction - and end up screwing up their natural ability when attempting to do so, (cough cough Lopez cough cough). 

The reason that most 1st round draft choices will never get more than a cup of coffee in the majors is because instruction is soooo bad prior to the minors, that 80% (and I might be generous here), of the kids being drafted, haven't gotten much good advice -- everyone from 1st round to 50th is effectively a blank slate, who is starting from scratch - and is getting a shot because they seem to have done well at a largely self-directed hobby.

Rivers may run dry in AA or AAA or make it all the way to the show before turning into Wlad.  Or, he could just be another in a long, long line of Piazza's - who were not 'naturals' - but had stellar careers while coming from extremely pedestrian roots.