Can it be defense? In Sean Gregory’s piece for Time Magazine this summer better gloves are painted as a likely cause of the change. It’s true that over the past few years there has been an increasing awareness of the importance of defense by general managers around the league, even ones not name Zduriencik, and if more good gloves are in the field (who presumably don’t hit as well) that could impact offensive production from both sides. Defense is typically credited with three things, a reduction in errors, a reduction in the percentage of balls in play which fall for hits and an increase in the number of double plays. On the last count we can basically ignore the role of defense in the scoring drought – the average AL team hit into only 1 more double play in 2010 than in 2009. While the average NL team hit into 4 more, again, the decline in scoring was far more pronounced among AL teams. As for errors, the average MLB team committed 6 more errors in 2010 – so that certainly can’t be a cause for the decline in scoring. For the impact of balls-in-play average a case can be made. In the NL, BABIP actually increased very slightly but in the AL it decreased from .3047 to .2996. If AL GMs are focusing on defense, it could be the case that a chunk of the decrease in scoring is due to those gloves preventing hits. Of course, the causality could be running the other way. BABIP seems to be influenced more by the batter than by the opposing team, and perhaps playing better defenders (with weaker bats) is affecting league BABIP through their noodle bats as opposed to golden gloves. Either way, if a preference for defense explains a significant piece of the drop in offense there is no reason to expect that to change in 2011.
Upon closer examination, that argument seems to break down: If we see that fewer ground balls are going for hits, we can definitely make the case that this is caused by better defense (or, potentially, a whole lot of luck), or better pitching or weaker hitting. However, a shortstop can’t possibly take credit for the fact that the ball was hit on the ground in the first place. Looking at the breakdown of batted balls in 2010, there was a real drop in line-drive percentage of a full percentage point – half of which went to increased ground balls and the other half of which went to increased fly balls. Since line drives are far more likely to fall for hits than grounders or flies, this drop explains the fall in BABIP completely. Whether that drop was caused by pitching, hitting or luck it certainly wasn’t caused by defense – unless the simple act giving plate appearances to ‘better’ defenders is causing an offensive swoon.