Arsenal midfielder Abou Diaby has undergone an ankle operation and will be out of action for up to 10 weeks.
The France international was troubled by the joint towards the end of last season and it forced him out of the pre-season tour of Asia and the club's training camp in Germany.
Diaby is likely to be sidelined until September, meaning he will miss the Barclays Premier League games against Newcastle, Liverpool and Manchester United, as well as the Champions League play-off.
"Abou had ankle surgery during the break," Gunners boss Arsene Wenger told Arsenal.com.
"Normally he should be back eight to 10 weeks after his surgery, which means the end of August."
Diaby's absence will come as a blow for Wenger, who is short of options in central midfield having allowed Denilson to leave for Sao Paulo on loan while doubt continues to surround the future of captain Cesc Fabregas, who remains a long-term target for European champions Barcelona.