Patrick Vieira has suffered a thigh injury which is threatening to rule him out of the start of the season.
The Inter Milan midfielder has picked up a knock to his left leg and faces a race against time to prove his fitness heading into the 2008/09 campaign.
The France international took part in a pre-season tournament on Tuesday which included AC Milan and Juventus, but has paid the price for his involvement.
Tests conducted by the Serie A club show that the former Arsenal man has suffered a strain just above the area which prevented him from representing his country at Euro 2008.
"I'm sorry but I remain optimistic," Vieira, who was also troubled by injury last season, told Inter's official website.
"I'll do everything to be available at the start of the season. I'm not giving up. Beating bad luck is one of my aims, along with winning lots more with Inter."
The injury blow to Vieira comes at the worst possible time for Jose Mourinho's men, as the reigning Italian champions have already seen their defensive options decimated during the close-season.
Walter Samuel, Cristian Chivu and Ivan Cordoba have all undergone surgery this summer, while Marco Materazzi picked up a knock in Turin on Tuesday.
The issue has got so bad that Inter president Massimo Moratti recently admitted that the club may be forced to dip into the transfer market before the new season gets underway on 31st August.