It effectively cost them a roster spot. In the long run, given the way 2010 turned out, it probably didn't matter. But at the time, we didn't know that. The Mets were still a contending team until early July. Perez's stubbornness could have been very costly. Anyway, whether the selfishness proved harmful or not, it's not an admirable quality. It certainly can be considered grounds for not liking him.