There must be a clause in the contract that allows the club to get rid of this guy if he doesn't play a game in, say, 5 years? Or what about his residency status - if he doesn't have a job, can he be deported?

I feel sorry for Diaby of course, and it'd be great if that clogger who injured him gets run down by a bus, but we need the money being wasted on Diaby to pay a player who can actually play. That's just common sense isn't it?