You could make a good case that Yankee shortstops have been the worst in baseball this season. You could make a good case--I have--that Yankee third basemen have been the worst in baseball this season. And I'm making the case here that Yankee left fielders have been the worst in baseball this year. They are 28th in batting at .224. They are last in on-base percentage at .269. They are 29th in slugging at .333. Vernon Wells had a hot April (.300 BA, .366 OBP, .544 SLG, 6 HR, 13 RBI) and since then has been awful. Zoilo Almonte has done nothing. Ichiro played 8 games in left and collected 6 singles in 30 at bats. Heck, the Marlins, whose primary left-fielder is the powerless Juan Pierre, have almost the same slugging percentage (.330).
What's amazing about this is that the Yankees have three positions that are absolute black holes, arguably the worst in baseball, and they're still five games above .500 and only 3.5 back in the wild card chase.