Everyone knows that Ryan Zimmerman's production in 2009 and 2010 has not been matched in 2011 and 2012. Can we identify the reasons why?
I'll just get into the numbers, starting with when he makes contact.
2009: 39.6 GB%, 41.6 FB%, 15.9 HR/FB%
2010: 41.2 GB%, 41.2 FB%, 14.0 HR/FB%
2011: 50.5 GB%, 33.8 FB%, 10.9 HR/FB%
2012: 53.7 GB%, 30.9 FB%, 5.6 HR/FB%
These trends are not fun to look at.
The ground ball rate was pointed out to me by Eno Sarris in his RotoGraphs chat Friday. After more digging, it turns out that's not the only negative trend. Fly balls go down when ground balls go up, naturally, but Zim is also hitting far fewer of those out of the park than he used to.
Additionally, thus far this year he's not getting the bump on balls in play that usually comes with more ground balls than fly balls, so his average has collapsed as well as his power. His batting average on balls in play in a season has never been lower than .295, but it is .262 so far this year. We can hope--perhaps expect--that this might correct itself eventually. We're still looking at a lot of singles and not a lot of extra bases.
Overall, his batted ball trends: very, very bad.
His walk/strikeout numbers are not as bad, at least on the surface, but they are not promising either.
He's striking out at a rate no worse than in his past (17.6% this year, 17.1% in 2009). So, on the surface, that's not really his problem, which is fortunate. However, he is swinging and missing at a career-high 8.5% of the pitches he sees. Oddly enough, last year he had a career LOW 6.5% in that stat, and it wasn't his greatest season, although he was certainly better then than now. But overall, strikeouts aren't his biggest problem as of now.
Meanwhile, his walk rate has also been trending downward the last few seasons. It peaked at 11.4% in 2010, and has gone to 9.3 and 8.5 since. So all three parts of the triple slash (average, on base, power) have been gradually sliding. It's not sudden.
Going deeper on one more level, we can check his plate discipline trends. If you need the definitions of the statistics below, please visit http://www.fangraphs.com/library/index.php/offense/plate-discipline/
2009 - 21.3 O-Swing%, 65.0 O-Contact%, 50.6% of pitches seen outside the strike zone
2010 - 25.9 O-Swing%, 68.7 O-Contact%, 54.4% of pitches seen outside the zone
2011 - 28.4 O-Swing%, 71.9 O-Contact%, 56.9% of pitches seen outside the zone
2012 - 29.6 O-Swing%, 67.4 O-Contact%, 56.0% of pitches seen outside the zone
Pitchers appear to be pitching around him more as time goes on, but he's swinging at those additional pitches out of the zone! Is this a pitch recognition problem?
We should consider that his 29.6 O-Swing% this year is still about league average (which is 30.0%). Nonetheless, the trend is bad and part of Zim's success in the past might have been due to his NOT swinging at those pitches out of the zone.
Overall, here are two more general thoughts.
First, Zim is probably either pressing (or hurt, which I'll get to) for the most part the past couple years. He's swinging at more and more pitches out of the zone and walking less over time. These can probably be fixed.
Second, and more alarming, his power hitting days look increasingly distant with every passing game. The ground ball rate is too high and the ball is getting out of the park less and less, even relative to the number of the fly balls he's hitting. And this has happened gradually, not tanked this year only.
Last thought: those possible nagging injuries. I'm not sure how much impact they might be having. It's unlikely that his 2012 injury is the sole reason for his struggles, because of the trends going back to 2010. And if those trends going back to 2010 are injury-related, that's a serious problem, because then it's unclear when or how he will ever get healthy.
Whether injury-related or not, this 2012 season so far is a serious concern going forward, since it appears to have been some time in coming. Either way, Ryan Zimmerman is a National till 2020, and we need him to get better in every way you can interpret the phrase.