Milan will be without Daniele Bonera for the start of the season after he fractured his kneecap against Valencia on Saturday.
The experienced defender could be out for up to three months with the injury, which was sustained as the Serie A side opened their International Champions Cup campaign with a 2-1 win at the Estadio Mestalla.
A Milan statement revealed that the 32-year-old will miss "70-90 days, barring complications".
His absence leaves the club with just two out-and-out centre-backs in their squad in the shape of Philippe Mexes and Cristian Zapata.
The Serie A outfit also announced that Robinho could be out for two weeks after suffering a thigh strain in the same game.
The Brazilian was forced off after just 27 minutes and is now a major doubt for Milan's UEFA Champions League play-off, the first leg of which will take place on August 20.
Robinho had looked set to leave Milan ahead of the new season, and re-join boyhood club Santos, but he opted to sign a three-year deal at San Siro after the move fell through.comments