Arsene Wenger will face renewed criticism for failing to strengthen his squad this summer after it was announced that Danny Welbeck will be out for several months.
The England forward has undergone surgery on a knee problem which has kept him out of action since April and caused him to miss the FA Cup final.
The 24-year-old, signed from Manchester United on deadline day in September 2014, last played for the Arsenal four months ago.
Despite hopes Welbeck would be able to recover from bone bruising around the knee, Arsenal announced in a statement on Thursday the player had needed an operation and was now set for an extended spell of rehabilitation.
Arsenal manager Arsene Wenger had hoped the forward would be available soon after the international break.
However, following an increased training schedule, it was decided surgery would be needed.
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A statement from Arsenal read: "Danny Welbeck has undergone surgery on his left knee after being unable to sufficiently step up his rehabilitation work.
"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."
With the decision to operate having come last week, there would have still been time for Arsenal to move in the transfer window to bolster the attacking options.
Arsenal had long been linked with a move for first Karim Benzema at Real Madrid and then Uruguayan forward Edinson Cavani from Paris St Germain.
However, the deadline passed with no further additions to Wenger's squad apart from veteran goalkeeper Petr Cech, who arrived earlier in the summer from Chelsea.
Arsenal recovered from losing their opening Barclays Premier League match at home to West Ham, winning two of the three games since.
Midfielder Jack Wilshere continues his recovery from a hairline fracture in the left fibula and could be back in contention when domestic action resumes at home to Stoke on September 12.