Unsurprisingly, Robinson Cano is the most valuable Yankee this season, in terms of fWAR (1.7). He's slowed down a bit from his hot start, but Robbie is still putting up a .378 wOBA. When you do that at second base you'll make yourself a high cost commodity, no matter how bad your defense is. It's the second name on this list that may surprise people. Once again, Brett Gardner (1.4 fWAR) rates as one of the most valuable Yankees, so long as you like defense. For fWAR watchers, this isn't as big a surprise as it seems. Whenever he's healthy, Gardner has always rated near the top of the Yankee heap in value because of his defense. In fact, Fangraphs says that Gardner has produced 14.9 fWAR between 2009 and 2013, inclusive. That makes him the 38th most valuable player in baseball during that time. That ranks just behind Curtis Granderson, and just ahead of Mark Teixeira. That feat is impressive enough, but it jumps up a notch when you consider that Gardner missed large stretches of 2009 and 2012. If you look just at 2010 and 2011, his last complete two seasons, Gardner ranks 12th in the game, just behind Matt Holiday and just in front of Adrian Gonzalez. Based on this it should come as no surprise that a healthy Gardner is once again adding value with his glove and his feet.
Is the value real? The fun part about analyzing Brett the Jet is that his value is contested. If you trust defense, then there's no question. From 2009-2013 he's the most valuable defensive player in the game, according to Fangraphs. He racked up that value despite missing so many games. But, if you feel the defensive metrics are at best shaky, which they are, then Brett's true value is less clear. He hits no home runs. He's a career .265/.352/.375 hitter. He's definitely fast, and steals bases with an 81% success rate, but other than that he doesn't shine on offense. To a baseball purist, it isn't clear where Gardner would rank.
For my part, I believe Gardner produces phenomenal value for the Yankees. Defensive metrics are spotty, but not when applied to outfielders. UZR essentially chops the baseball field up into units and sees how rangy a player is. This doesn't work well for infielders, especially Catchers and First Basemen, but it is particularly effective in the outfield where it is clear if a player is running a fly down or not. In addition, Gardner's defense passes the eye test. I'm not a big fan of the eye test in general, but when my eyes reinforce what the numbers tell me I become that much more confident about the numbers themselves. The numbers say Brett is a defensive whiz. My eyes agree.
The beauty of Gardner is that his skills will never command an eight figure contract. The Yankees know his value. He probably suspects his value. But without a line item in the box score to point to, Gardner's side isn't left with a lot of room to negotiate. That will keep his value low. So long as Gardner can remain healthy (given his history and style of play, not guaranteed) he should be a mainstay in the outfield for years to come, and at a bargain cost.