Brett Gardner's presence in the outfield should improve the Yankees' ERA and help them win games. (Image: Joe Nicholson-US PRESSWIRE)

The Yankees and the Importance of Defense

Defense is one of the most underrated and overlooked aspects of baseball. For one, it’s difficult to measure — we can’t easily determine a player’s defensive ability just by looking up his player page. Secondly, it’s not always obvious how important defense is to the game. Hitting is easy, because one can clearly see how a hit can turn into a run, and how better hitters get more hits. But, apart from fielding percentage, there is no discrete way to measure good defense. While fielding percentage is certainly an aspect of defense, one cannot deny that range, positioning, instincts, arm, etc., are also essential to defense, and possibly more important than preventing errors.

This is all a way to say that defense should be talked about more. For the New York Yankees, in particular, defense has been an important component of success — or, at the very least, pitching success. To illustrate this importance, consider the following image, which graphs ERA- (ERA normalized to the league so that 100 is league average and 90 is 10 percent better than average) alongside team fielding, which is measured using UZR for the last 12 years. UZR, or Ultimate Zone Rating, is a very complicated and intricate metric that measures, essentially, how well a player — or team — converts batted balls into outs. It has a lot of flaws, but over a large enough sample size, it is fairly accurate at measuring defensive value.

As you can see, the Yankees’ fielding has been pretty awful for the past decade or so, hitting a low point in 2005 with an astonishing 140 runs, or about 14 wins, below average! That’s a pretty astonishing number, one that makes it pretty difficult to field a playoff team; unless, of course, you have a fantastic offense and solid pitching, like the 2005 Yankees did.

From 2005 to 2011, however, the Yankees’ defense consistently and rapidly improved, reaching positives in 2011 for the first time in 13 years. As you can see, the Yankees’ ERA- followed, steadily improving almost every year since 2004. The two data sets ended up having a correlation of -0.57, which means there is a relationship there, albeit not an extraordinarily strong one.

 Of course, there are a lot of other factors in play here. ERA is directly correlated to BABIP, LOB%, K%, BB%, HR/9 and so on. Defense, however, presumably only affects BABIP and LOB%, since good fielding turns more batted balls into outs, which makes it easier for pitchers to escape jams. Let’s see if the above improvement in ERA is actually due to a better FIP (strikeouts, walks and home runs) rather than defense:

Nope. Looks like, as far as the peripherals go, Yankee pitching hasn’t really improved significantly over the years. It has been better in the past two years, but overall, we don’t see the same steady decline as with ERA.

Where we do see a strong improvement, however, is in the strand rate, or LOB%, for the Yankee pitching, which has increased every year since 2004. Part of this is due to a league-wide increase in strand rate due to a rising strikeout rate in baseball; however, the Yankees’ drastic improvement in stranding runners cannot only be explained by an increase in strikeouts. And the sample size is large enough that it isn’t just a result of good luck either.

The most probable explanation left is defense. The improvement in defense has helped Yankee pitchers to pitch out of jams more easily by turning more batted balls in these situations into outs. In turn, the Yankees have given up up fewer runs, despite relatively unchanging peripherals.

Long story short: defense matters, and it has helped the Yankees prevent runs from scoring over the years. Their defense declined a bit last year, and we saw that decline through a worse ERA. Brett Gardner‘s presence in the outfield should make a significant impact in this regard. By tracking down balls that would normally fall for hits, Gardner will prevent runs from scoring, improve the team ERA, and win games.

So let’s not ignore defense, even though MVP voters seem to have forgotten its importance (sorry — couldn’t resist). Even if it only adds or subtracts a couple wins over a full season that can and probably will make the difference in a competitive AL East.

All stats taken from FanGraphs.

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