Fiorentina forward Giuseppe Rossi will need further surgery on his right knee, the club confirmed on Monday.
After consultation with a specialist in London, it was confirmed that an arthroscopy would be needed "to resolve the current problems of overburdening the right knee."
Rossi underwent surgery for the second time in January, but despite returning for the final few matches of last season, he was not considered fit enough to appear at the World Cup by then Italy coach Cesare Prandelli.
During examinations of a muscular injury in preseason, a weakening of the knee that had been operated on was discovered, resulting in an enforced break.
Tests a week ago revealed an improvement, but also the necessity for more tests, amid fears more surgery would be required.
"The [surgical] intervention will be performed during this week following another consultation, requested by the player with Dr Steven Singleton, assistant to the professor Richard Steadman in Vail (Colorado)," a statement on the Serie A club's website said.
Rossi missed Fiorentina's league opener against Roma on Saturday and was left out of the latest Italy squad, although national coach Antonio Conte has said he is "counting on" the former Villarreal and Manchester United forward.
Fiorentina have given no indication of how much longer Rossi could be sidelined for.