It's because players like Revere tend to have short careers that end brutally. I'm not against Revere as a stopgap; what I'm against is having him through his late 20s and then paying him a bunch of money just as he falls on his face (see Figgins, Chone). The Twins can keep Revere for a year or two but if they're smart, they'll ditch him the moment his value is high and they have someone else to play the position. I like Revere, but I'd agree he has his drawbacks. He slugs below .700, and his OBP needs to improve. I'd choose Span over him for sure, but as mentioned, it's less about him than it is about depth in the outfield behind him. Did you really expect Revere to hit 40 doubles and 10 home runs?