According to most defensive metrics, Curtis Granderson had an awful 2012. Even the eye test told a tale of a center fielder misplaced on a team filled with more adept outfielders. The collective online Yankee community is in agreement that sending Granderson to left field, and giving him less area to cover, will help stop his defensive regression. The Yankees don't agree.
When a player is visually struggling, you usually go to the stats to see how long and how poorly they've played. When a player suddenly puts up awful numbers, you usually go to the video to see why the numbers are degrading. This generation of baseball enthusiasts is lucky enough to have the numbers, analysis, and video available instantaneously on the internet, and it allows us to judge team's decisions in a more scientific and thorough way than ever before. But when it comes to defense, the amount of data and the way we analyze it is still in its infancy.
To give you an idea of the reliability of today's defensive statistics, Curtis Granderson's 2012 -18.2 UZR/150 was the worst in all of baseball, while his RZR ranked well above average at 10th overall, placing him between BJ Upton and Andres Torres. You can also trace this yearly, and see that his UZR/150 has fluctuated from 7.9 in 2010 (the fourth best center fielder), to -5.3 in 2011 (12th ranked center fielder), to finally the worst ranked center fielder last season. This isn't the first time UZR/150 has had mixed feelings, in 2006 and 2007, Granderson put up a 13.6 and 14.6 UZR/150, followed by a 2008 that dropped to -11.9.
If you're looking for any sort of consistency, RZR remained far more reliable throughout his career. Since 2006, the highest fluctuation from his career .913 RZR was in 2009, when he put up an outstanding .936. If you're one that believes in RZR, Granderson's defense has been above average (.896 is your average zone rating in center field), and in 2012, his defensive range was actually very good. Of course, debating between UZR and RZR is not the point of this article.
For most people, the decision to send Granderson to left field is a "no-brainer", when that's simply not true. The data from 2012 tells two different stories, and that's because the math behind defense typically needs a sample size of around three years or more to start to become meaningful. The fact is that we don't know how Granderson performed in center field in 2012, but we know that in his career, his defense has been slightly above average.
The Yankees likely have much more data to help them make their decision, and that's why it's hard for us fans to question what they do defensively. When asked about how he'll make his decision, manager Joe Girardi had this to say,
“How they play individually, but how the tandem works together in covering from right-center all the way over,” Joe Girardi said. “Reads on the ball, jumps on the ball, throws, decision making, everything. … I don’t know how much defensive metrics are going to give me (to help make the decision). For me, it’s visual, and just something I thought might help us.”
Granderson will be 32 years old this season, and defensive decline will continue to be something to worry about. Center fielders and short stops see the biggest rates of regression of any other offensive position. The Yankees have a much better idea of how Gardner and Granderson play defensively though, and there are a number of factors that could make the switch a net negative in the end. It's possible that Granderson gets poor jumps or reads on balls hit to his left, or perhaps Gardner has poor reads on balls hit to his right. Either way, the Yankees' discomfort with making this switch likely comes from numbers and scouting, rather than a tenacious agenda against listening to fans. In the end, it's hard for us to argue against pulling the plug on the position swap when our two best defensive metrics can't even decide if Granderson had a good or bad year.