By Terry Daley ROME March 8 (Reuters) - Mario Balotelli came off the bench to help fire 10-man AC Milan to a hard-fought 2-0 win at Genoa on Friday, strengthening their grip on third place in Serie A ahead of Tuesday's Champions League clash with Barcelona. Balotelli netted the decisive second goal on the hour after replacing the injured Giampaolo Pazzini, who scored Milan's 22nd-minute opener only to be substituted three minutes later.