One f***ing play? When since one example condems a player? Let's go with your logic. The following players are lackluster:
Manny Ramirez
Coco Crisp
Trot Nixon
Mark Loretta
I'm sure countless others would fill this list.
Pena isn't a great RF. But, c'mon? Just because the guy didn't think he could beat Coco Crisp to the ball, doesn't mean that he doesn't care.
(By the way, Pena's first game in RF was against the Orioles. No error was recorded, nor was a double recorded.)