Arsenal midfielder Abou Diaby has been ruled out for up to nine months with a torn anterior cruciate ligament.
Diaby, who signed for Arsenal from Auxerre for around £2 million in 2006, has been plagued by injuries during his career, and in the current campaign he has started just ten Premier League games for the club.
The Frenchman played 71 minutes of the Gunners' 2-0 win at Swansea but was not involved for his country during the international break.
And, ahead of this weekend's home match against Reading, it has been confirmed Diaby, 26, is set for a lengthy spell on the sidelines, which will come as a blow to the side's top-four ambitions.
A statement on Arsenal's official website read: "The club can confirm that Abou Diaby injured his left knee in training on Wednesday and subsequent scans have confirmed that he has torn his anterior cruciate ligament.
"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."
A series of injuries have also prevented Diaby for featuring for his country since he scored the only goal of the game in Les Bleus' opening 2014 World Cup qualifier against Finland last September.
Guy Stephan, France assistant coach, told RMC radio that Didier Deschamps, who has publicly declared his admiration for Diaby's talents, had been expecting to draft the Arsenal man back into the international set-up.
"It's bad news, because Abou contributed a lot, notably in Finland, because he scored the matchwinner," he said. "We hoped he'd be back soon. It's terrible, firstly for him and then his club and the French national team. He's had a lot of muscle problems, and he was doing his utmost to get back into shape. Unfortunately, he's going to be sidelined for many months."