Wilin Rosario was one of the more interesting story lines coming into the year. He displayed big time power in 2012, smacking 28 homers and posting an isolated slugging percentage of .260 (ISO is slugging minus batting average; basically, it's extra-base power).
But there were warts in his game; he allowed a ton of passed balls and wild pitches, while displaying well-below-average patience at the plate.
The book on Rosario is that he's susceptible to the breaking ball. Accordingly, he's seen the second fewest fastballs in all of Major League Baseball at 44.1%. Josh Hamilton edges him out by a tenth of a percentage point, and Josh Hamilton swings at breaking balls that he sees in nightmares. But according to Fangraphs' pitch values tables, Wilin has been above-average against sliders and cutters, while being only slightly-below-average against curveballs. Those pitches are supposed to get him out, but he's been more than holding his own.
Despite this, Rosario's hitting basically the same as he was last year, when he was a pumpkin against sliders. Actually, his power is down somewhat, from slugging .530 last year to .496 this year (on base percentage is basically identical). This could just be some natural regression; after all, he's still on pace for about 25 dingers.
Somewhat incredibly, his walk rate is actually down this year. Rosario, always a free swinger, walked at a 5.9-percent clip last year; in 2013, it's down to 3.8 percent. His average (and by proxy, on-base percentage) is buoyed by a .331 BABIP. His strikeout rate is identical, so while he's hitting breaking pitches better, he's not really laying off of them. So far this approach has worked for him; Wilin's never been a below-average hitter. But it's still a trend to keep watching.
Defensively, the Bull has taken a small step forward. He's on pace for many fewer passed balls this year (21 in 2012, nine so far in 2013) and slightly fewer wild pitches (63 last year, 40 so far in 2013). His game-calling also seems to be much improved; the pitching staff is having a fantastic year with Rosario catching the majority of the innings. Keeping his bat at catcher is one of the most important parts of maintaining Wilin's value.
Rosario could have had any outcome this year. He might have been exposed to breaking balls. His defense might have further eroded. He might have taken a big step forward in pitch recognition and become an elite bat. Instead his year has been ... basically identical to last year. That said, it's easy to fall into a sophomore slump (hi Josh Rutledge!), so seeing Wilin hold his own is a welcome sight. Hopefully he finishes the year strong.
Notes about last night's game. Rafael Betancourt's elbow injury is the big blow; if the ligament is really torn he'll be out for the rest of the year, and possibly most of next year. This is seriously bad news for a 38-year-old. Hopefully he makes it back to the mound at some point. Betancourt's been one of the best relievers that Colorado has employed for multiple years.
Ryan Braun admitted to his PED use. Whatever.