Fiorentina said that Rossi "will require diagnostic arthroscopy surgery to resolve the current problems in his right knee."

They added that he will have the operation later this week after a consultation in Colorado.

Rossi, 27, has already ruptured cruciate knee ligaments twice before, missing almost two years of his career as a result. He did not go to the World Cup after suffering a recurrence last season at a time when he was the leading scorer in Serie A.

The former Manchester United and Villarreal striker, who was born in the United States, has been capped 30 times by Italy