Danny Welbeck is likely to be out until at least Christmas after Arsenal concealed his need for a knee operation while they tried in vain to sign a striker before the transfer window shut.
Welbeck has had an operation to the articular cartilage of his left knee after what was initially thought to be bruising did not heal during a prolonged period of rest.
News of Welbeck's injury has deepened the frustration among supporters at the failure to sign a striker during the transfer window but Arsene Wenger was always only interested in adding a player of proven world-class experience. France striker Karim Benzema was his preferred target but Real Madrid were unwilling to contemplate a sale unless they themselves made a major signing.
Wenger also inquired about Paris St-Germain forward Edinson Cavani, but he too was unavailable and it was ultimately decided not to use a significant part of the transfer budget on someone of similar standing to Welbeck. Charlie Austin, the Queens Park Rangers forward who scored 18 Premier League goals last season would have been available for pounds 15?million.
Wenger believes that Olivier Giroud, Alexis Sanchez, Theo Walcott and Joel Campbell provide sufficient centre-forward options to challenge for the Premier League title, although his gamble is compounded by the lack of certainty over when Welbeck might be fit.
Welbeck has not played since the end of April, despite Wenger's initial hope that he had suffered only a short-term injury. He then missed England's final international matches of last season in June and did not return for the club's pre-season training in Singapore. Wenger continued to believe the injury was short-term during the summer and, even last week was saying that he expected Welbeck back in training after the international break.
The decision to have surgery was made only last week but Arsenal clearly did not want the news out made public given that the transfer window had not shut and they might be negotiating with another club for a player. They also wanted to wait until Welbeck's operation was actually completed this week.
The timescale of "months" remains vague and, while Christmas is considered a realistic estimate, it would be no surprise if Welbeck did not return until next year.
Welbeck was a deadline-day signing from Manchester United last summer and scored eight goals for Arsenal last season. "Danny Welbeck has undergone surgery on his left knee after being unable to sufficiently step up his rehabilitation work," an Arsenal statement said.
"The striker has been working throughout the summer to recover from the injury sustained at the end of April. It had been hoped he would avoid surgery, but after increasing his training workload, the injury to his cartilage did not respond as well as hoped and the decision was taken last week for him to undergo surgery by a leading specialist in the field. Danny is now expected to be out for a period of months and everyone at Arsenal wishes him well."
Arsenal were the only club among the leading European leagues not to sign a new outfield player this summer. Jack Wilshere is also continuing his recovery from a hairline fracture to his left fibula and is due back in training ahead of the home Premier League match against Stoke City on Sept 12.