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 in training on Tuesday and is unlikely to feature for the Gunners until next year.
Arsenal are also currently without Jack Wilshere due to a recurrence of an ankle problem that is feared by club officials 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.