ROME (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.

Milan were under extreme pressure after Kevin Constant was sent off in the 65th minute for lashing out at Genoa defender Cesare Bovo, but their defence held firm in face of a spirited attack led by the impressive Marco Borriello.

Milan now have 51 points, two behind second-placed Napoli and four ahead of Inter Milan and Lazio.

Genoa, who were left fuming after two big penalty shouts were turned down in the first half, remain in 17th place on 26 points, five above the relegation zone.