The Italy international will not feature for the Rossoneri at the weekend, when they take on Serie A's third-placed team, due to physical problems
The former Manchester City attacker picked up a leg injury earlier this week, and will not be recovered in time for Saturday's encounter at San Siro.
"Balotelli will not be available due to a bruised tibia. Unless something miraculous happens between now and Saturday morning, he will not feature against Lazio," Allegri stated at a press conference.
The 22-year-old striker's absence will come as a huge blow to Milan as he has become a key player for the Rossoneri since his winter move.
Balotelli has scored four goals in as many Serie A appearances for the 2011 Italian champions since his estimated €22 million switch.