The Orioles' highly touted young catcher has not exactly caught fire since joining the big league club in 2009. He sported a wOBA on .330 in 2009, but regressed considerably in 2010--posting a wOBA of .303. Matt Wieters showed solid power in the minors, sporting an ISO of .199 or better at every level. That power has failed to materialize in the bigs, leaving Wieters with ISO's of .124 and .128 in 2009 and 2010 and correspondingly lack-luster SLG (.412 and .377).
2010 was seemingly a worse year for Wieters than it needed to be. If we look at the batter regress tool, Wieters should have posted a wOBA of .360 based on his K% and BABIP in the bigs (granted, this was only one year but those metrics were consistent with his minor league career). Wieter's BABIP dropped from .356 to .287, one of the largest drops for an everyday player last year. Even assuming an adjustment period and that a .360 wOBA may be too big a leap (which it was), we would have expected Wieters to post a better 2010 than .303.
What's interesting is that Wieter's low BABIP looks to be just as much a function of a bad approach at the plate as it is bad luck. My interpretation of the numbers is that Wieters is trying too hard to avoid striking out, which is driving down his impact on balls in play.
(Note: I have probably seen about four Wieters' at-bats in my life. This is purely about interpreting the numbers, so all caveats apply.)
From 2009 to 2010, Wieters swung at more balls out of the zone (30% vs 25.7%) and put more of those balls in play (roughly 71.4% vs. 61.3%. This suggests to me that Wieters is scuffling at the plate, making poor contact on balls out of the zone. This idea is bolstered by the fact that his RAA on fastballs in 2010 was -1.1, down from 6.6 in 2009. Moreover, Wieter's traded lots of line drives for ground balls in 2010--his LD% dropped by 3.1% and his GB% increased 4.5%. So while he put more balls in play, he didn't do so in a way that was likely to be productive.
Dan took a look at Wieter's batted balls in 2010 and noted the same trend in terms of less line drives and productive balls in play. Wieters did lower his K% by about 3%, but that isn't necessarily a good thing. His BABIP on two-strike counts was only .266 in 2010 as opposed to .333 in 2009.
All told it suggests to me that Wieters may have been too concerned with avoiding strikeouts. If so, Wieters' drop in BABIP could just as easily be explained as the result of weakly hit balls and not simply bad luck.
The good news is this suggests there is still some upside to Wieters offensively. He may not be Joe Mauer, but he has the potential to be a 3+ WAR player if he can recapture his LD%. This may mean he should focus less on avoid K's and more on driving the ball. There's lots of work suggesting that, with a hitter like Wieters, the marginal gain from reducing strikeouts is far outweighed by the gain from increasing BABIP.
-------
Data from FanGraphs