Arsenal midfielder Abou Diaby has been ruled out for 'eight to nine months' with a serious knee injury.
The France international tore the anterior cruciate ligament in his left knee at training on Tuesday and is unlikely to feature for the Gunners until 2014.
Arsenal are also without Jack Wilshere due to a recurrence of an ankle problem and it is feared by club officials that it could result in another long-term absence for the England international.
A club statement read: "Following consultations with specialists, Abou will undergo surgery to repair the injury in the near future.
"Abou is expected to be out for around eight to nine months.
"The thoughts and best wishes from everyone at Arsenal are with Abou, and we all wish him a successful recovery."
Diaby made 14 appearances this season and has previously endured long-term layoffs due to ankle and thigh injuries.