AC Milan defender Andrea Conti has been ruled out for six months after damaging the anterior cruciate ligament in his left knee.
The Italy international has made five appearances this term after arriving from Atalanta in a transfer window of heavy recruitment at San Siro.
Conti sustained an ankle injury on Italy duty two weeks' ago, but has suffered a much more serious issue upon his return to training with the Rossoneri.
"Andrea Conti underwent diagnostic procedures this afternoon. The results have shown an anterior cruciate ligament rupture (ACL) to the left knee," a Milan statement read.
"The Italy international will undergo knee arthroscopy surgery for the ACL reconstruction [on Saturday].
"His recovery time is estimated to be six months."
Milan's city rivals Inter sent well-wishes to the defender via Twitter, posting: "Get well soon Andrea #Conti! Hope to see you back for the second #DerbyMilano in a great match."