Let him come.
In my opinion, the squad we've got now is too soft, everyone comes across as too nice and friendly. Most sucessful teams need to have at least one 'win-at-all-costs' prick on the pitch that keeps opposition on their toes and eggs on the rest of the team - Rooney, Terry, Vieira, Cantona, Keane, Gerrard etc.
At the moment the team seems to just roll over and play dead at the first sign of a challenge.
I in no way condone his off-pitch behavior, but he's had his stint in prison now and there's every chance that it brought everything into perspective for him regarding how good he's actually got it.