The veteran defender picked up the knock against Barcelona in the Champions League in midweek, and will be replaced by either Daniele Bonera or Philippe Mexes against Chievo.AC Milan have confirmed that veteran defender Alessandro Nesta will be sidelined for a month with a hip injury.\"The prognosis, unless there are complications, is about one month,\" a statement on the club\'s official website reads.The 35-year-old was replaced after 66 minutes in the clash with the European champions by Daniele Bonera, who is set to fight it out with Philippe Mexes for a place alongside Thiago Silva in the Scudetto holders\' back line.Nesta joins Mathieu Flamini, Gennaro Gattuso and Antonio Cassano on Milan\'s treatment table.The Italian champions are three points behind current Serie A leaders Udinese, but can go back to the top of the pile if other results go their way over the weekend.The centre-back picked up the knock against Barcelona in a 3-2 defeat at the Giuseppe Meazza in midweek, and will miss the Rossoneri\'s game against Chievo on Sunday.