A quick look at what A-Rod has done so far this year

Behind the scenes here at TYA, and his awful start have gotten a lot of attention lately. Moshe illustrated why perfectly on Tuesday. In light of this, I thought I’d take things in a more positive direction and examine the performance of another player the Yankees needed to bounce back this season, one who’s almost as old, and a lot more important: . The synopsis of this post is that so far Alex has been a beast. His wOBA in 34 plate appearances is .486. His ISO is .393. While its fun to pretend, the fact of the matter is that A-Rod won’t sustain these numbers for the remainder of the season. Still, that doesn’t make it any less interesting to pull the curtain up and examine how he’s gotten off to this great start.

Before I go further, I need to digress momentarily and acknowledge my own post from Tuesday. I was careful to mention A-Rod’s plate appearances in the first paragraph to demonstrate that technically Alex has given us a large sample of data to work with. However, I also want to elaborate on two important points from the comments to shed some light on why the numbers in this post needed to be taken with a massive dose of salt. The first point came from the commenter Damian, who correctly pointed out that most statistical inference assumes that the sample of data is randomly generated, which A-Rod’s early season at-bats are not.

The second point came from my fellow TYA writer Moshe, who pointed out that if a large sample has a large standard deviation the sample may still not be suitable for drawing conclusions. Given that A-Rod has been hitting out of his mind, it is probably safe to suggest that his numbers so far this season have a naturally high variance. Now that we’ve established all the statistically valid reasons (that I can think of at the moment) why we can’t read too much into A-Rod’s season thus far, let’s take a closer look.

The table above contains two sets of data, both taken from Fangraphs. The top level focuses on A-Rod’s plate discipline. Moving from left to right, it contains the rate at which he has swung at pitches outside of the zone this season, the rate at which he has swung at pitches in the zone, the rate at which he has swung, his contact rate in the zone and his contact rate out of the zone. The second set of data show the rate of runs above replacement level A-Rod would generate against the fastball, slider, cutter, curveball and changeup for each 100 of those pitches that he sees (I used the rate stats to compare across seasons).

A-Rod has been able to do his damage so far this season with improved discipline, improved discipline that is almost certainly unsustainable. While his rate of swinging outside of the zone is more in-line with what he’s done in seasons before 2010, he’s swinging less in general, even at pitches in the zone. That may be fine and good against a handful of pitchers that Alex sees well, but expect that swing rate to creep up as the season goes on, taking his rate at swinging at pitches out of the zone with it.

The other thing that first batch of data tells me is that Alex is locked in right now, and picking his spots. He’s swinging less at everything, but hitting almost everything that he sees in the strike zone. As the season progresses that rate will come down, and he’ll begin making contact more on pitches that fool him out of the zone.

In the meantime, while Alex is so locked in, he’s crushing … well, almost everything. The most encouraging stat is his dominance against the fastball so far. A part of his struggles last season were due to a slight decline against the fastball. He’s bounced back in style this season. While his rate of 5.31 runs above replacement is by no means sustainable for the season (look at how much better that would be than his 2007 season), he has a comfortable margin built in there for regression. He could slow down considerably and still find himself on pace for one of his better years in pinstripes.

Of the remaining pitches, Alex has seen more than 10% sliders, curves and changeups and only 1.4% cutters. While it is informative that he has done well so far against the slider and badly against the curve and change, it is not all that important. Throughout his career Alex has seen a majority of fastballs (60.3%, according the data available on Fangraphs) and crushed them to the tune of 2.14 runs above replacement for every 100 that he has seen. The rate of 59.4% fastballs that he’s seen so far in 2011 is right on his career average, so it is encouraging that he is positively annihilating them. With any luck, this augurs well for a few months from now. I’ll gladly trade struggles against the changeup if Alex continues to clobber the heater.

Finally, Alex’s walk and strikeout rates are phenomenal so far this year, and therefore almost certainly unsustainable. His walk rate is 14.7%, compared to a career rate of 12.0% and a measly 9.9% last season. His strikeout rate is 14.3%, compared to a career rate of 20.8% and a 2010 rate of 18.8%, which was his best showing since 1998. As the season progresses and Rodriguez hits a rough patch, that strikeout rate is jumping up. I’ll be paying closer attention to the walk rate. His current walk rate would be his second best since 2000 (he managed 15% in 2009), but it is not as materially out of line with his career norms as the strikeout rate. It was also the walk rate that killed his overall performance in 2010. Alex doesn’t have a ton of room to regress downwards from 14.7%, but anything between 12% and 13% would be in line with his standards as a Yankee, and indicative of return to form season.

In conclusion, there are no conclusions because while we have a large sample of data it is almost certainly not randomly drawn nor does it demonstrate evidence of having a variance small enough to be used for statistical inference. That being said, anecdotally there are encouraging signs here. In the early going, for a player with a reputation for starting strong I’d hope to see several statistics well above what Alex has done for his career. The good news is, not only is he right there, but he’s well above his 2007 performance in terms of both his performance against the fastball and his walk rate. Both numbers will come down, but hopefully they’ll come down gradually, giving Alex plenty of opportunities to put together the kind of season he’s teasing us with after so few games.