Andrea Bertolacci picked up a knee injury in AC Milan's friendly defeat to city rivals Inter on Wednesday, the club have confirmed.
The midfielder lasted just 14 minutes of the clash - for the Luigi Berlusconi Trophy - at San Siro before being replaced by Jose Mauri.
Milan lost the game 1-0 after Geoffrey Kondogbia's early opener, and afterwards the club confirmed the news of Bertolacci's injury.
"AC Milan communicates that during the match with Inter as part of the 24th edition of the Luigi Berlusconi Trophy, Andrea Bertolacci suffered a heavy knock and bruising to the left knee," a brief statement read.
"The exams carried out have ruled out intra-articular lesions. The player will be re-assessed in the coming days."
Meanwhile, head coach Sinisa Mihajlovic was full of praise for 18-year-old defender Davide Calabria, who played the second half of Wednesday's defeat.
"He is doing well and he has always held his own every time he has been given a chance. I am very happy with him," Mihajlovic said.
"An opening goal always conditions a match, but as the match went on we gave away very little. They had one shot and scored one goal. We meanwhile had a lot of chances.
"We didn't take our chances while Inter were good and lucky at not conceding. We weren't.
"We have to evaluate a lot of factors and the injuries. In four days' time we have another match and we face Sassuolo. We will prepare well and try and give our best."
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