Arsenal will be without England forward Danny Welbeck for several months after he underwent surgery on a knee problem.
The 24-year-old, signed from Manchester United on deadline day in September 2014, last played for the Gunners in April, missing both the FA Cup final and end-of-season internationals.
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.
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.”