It's because he's being asked to play out of position (SS) in a high injury spot without a long term contract in a contract year.
He was never going to be more than a stopgap at SS anyway, and we'd have replaced him in 2011. And he (like DJ) would have bolted at the beginning of this offseason if it weren't for the fact that 5th year players were RFAs instead of UFAs in the last year of the CBA.