Midfielder Abou Diaby will miss the start of Arsenal's season after having ankle surgery during the summer.
Diaby, 25, has been troubled by the injury since the end of last season and was absent from the club's summer tour of Asia and a training camp in Germany.
Manager Arsene Wenger expects Diaby to miss league matches against Newcastle, Liverpool and Manchester United.
"Normally he should be back eight to 10 weeks after his surgery, which means the end of August," said Wenger.
Arsenal travel to Tyneside for their Premier League opener on 13 August, before a home match against Liverpool on 20 August and a visit to Old Trafford on 28 August.
After taking only five points from their last six games last season, which saw them slip down to fourth place after being well-placed for a title challenge, Arsenal also face a two-legged play-off to qualify for the group stage of the Champions League.
Diaby will also miss those matches, against as-yet-unknown opposition, on 16 or 17 August and 23 or 24 August.
The Frenchman's absence for a tricky start to the Gunners' league programme will be exacerbated by Denilson's departure to Sao Paulo on loan.
The situation could get even worse for Wenger with the possible loss of further midfield personnel before the close of the transfer window.
The future of captain Cesc Fabregas, a long-time Barcelona target, is still uncertain while Samir Nasri has been linked with a move to either Manchester United or Manchester City.
And occasional winger in an attempt to clear up a recurring ankle problem while 19-year-old Conor Henderson has been ruled out for the first six months of the season with a knee injury.