Originally Posted by Scrap Irony
He doesn't have to be league average and doesn't project to be so.
However, it could certainly happen that he grade out as league average over the course of one season.
1) One season is a small sample in terms of UZR. A couple nice OOZ plays and taking charge between Choo and Ludwick by grabbing all the balls in the gaps that he can get to might help.
2) Familiarity with the position may mean less "vapor locks", as he's played CF pretty much his entire life and knows the position as well as any. No (or very few) errors would boost his UZR as well.
3) Bruce has a great arm. He could very well lead all CFers in assists by a wide margin. (This depends, IMO, on Cespedes' position in Oakland.) That in itself could also boost his defensive WAR by a fairly large margin.
I'm not saying he's a good bet, but it's within the realm of possibility.
The only way either of those guys grade out as league average is due to the fact that defensive metrics are still in their infancy and are incredibly flawed. Also, everything you said for Bruce could just as easily apply to Choo. Why move Jay in 2013 if the plan is to move him back to RF in 2014? Why not just let Choo be the guy to play out of position?