That the Reds somehow lose an elite defensive player with this trade. Not even close. Stubbs is a fast guy. That is it. He is good from gap to gap because of his one God-given ability. He's subpar on balls hit short right at him, and borderline awful on deep balls hit right at him. (Granted, that's the toughest play for any OF.) Arm is average at best. We're not talking about losing 1987-caliber Eric Davis here.
The Reds' defense will be A-OK. There may be one ball every week or so that Choo (or whoever) doesn't catch that Drew Stubbs would have. And there might be one they come up with that he wouldn't.
