Laurent Koscielny: Formed strong partnership with per Mertesacker last season

Arsene Wenger has ruled out key Arsenal defender Laurent Koscielny for another four weeks - at least.

The centre-back has missed his side's last two games with a chronic Achilles problem which forced him out of France's recent internationals.

Wenger admits he does not know when Koscielny will be back, but it will not be before next month's Saturday Night Football game against Manchester United.

Arsene Wenger says Theo Walcott will not play against Sunderland this weekend. The winger will play for Arsenal under 21s to improve his fitness Arsene Wenger says Theo Walcott will not play against Sunderland this weekend. The winger will play for Arsenal under 21s to improve his fitness

Speaking at his press conference ahead of Saturday's trip to Sunderland, Wenger said: "I cannot give you any date. I hope he will be available after the next international break."

Koscielny's partnership with Per Mertesacker helped Arsenal keep 17 clean sheets in last season's Premier League, but only Aston Villa have failed to score against them in the league this term.

The Frenchman's absence leaves Wenger with only Mertesacker as an established senior centre-half.

His other options are teenager Calum Chambers, who was bought as a right-back, and second-choice left-back Nacho Monreal, who has filled in alongside the German twice in the past week.

Arsenal are without Mathieu Debuchy, Mesut Ozil and Olivier Giroud long-term, while back-up goalkeeper David Ospina was this week ruled out for up to three months.

Theo Walcott is close to returning after nine months out, although Wenger may wait until next week to involve the forward.