AC Milan hitman Alexandre Pato is facing another spell on the sidelines after aggravating a niggling thigh injury, the Serie A club said. The 20-year-old Brazilian has just returned from injury in last weekend's draw with Napoli, but he only lasted for 15 minutes on the pitch. Milan have confirmed that their top scorer suffered a muscle tear, which means he could be out for a further three weeks. Pato has been struggling with a troublesome thigh throughout the current season, raising questions over his availability in Dunga's roster for the World Cup.