A 26th-minute goal in the forward's first start for six months helped the champions to a 4-1 win at Siena on Sunday and they stayed three points adrift of Juventus as the leaders walloped Novara 4-0.
Three games remain and second-placed Milan host mid-table Atalanta on Wednesday desperate for Juve, chasing their first Serie A title since a 2006 match-fixing demotion, to slip up at home to third from bottom Lecce.
"He really has been very strong. He has not given up for one moment, he has come to the Milanello training ground and done exactly what he had to do. I didn't expect a goal immediately," club doctor Rodolfo Tavana told reporters.
"We wanted to make sure he could return to the pitch healthy and with no risks."
With the top two expected to win on Wednesday, focus will quickly turn to Sunday's derby between Milan and resurgent Inter who have rocketed up the league under new coach Andrea Stramaccioni and lie joint third with three teams.
Lazio will be without suspended defender Andre Dias and goalkeeper Federico Marchetti after bizarre scenes at the end of Sunday's 2-0 defeat at Udinese.
Visiting players heard a whistle in the crowd and thought the game was over, only for Udinese's Roberto Pereyra to score the second goal in injury time, leading to an unsavoury fracas and Dias's dismissal.
