Arsenal's injury concerns in defence have grown with the news that Sokratis Papastathopoulos has been ruled out for a month with an ankle problem.

Sokratis and fellow centre-back Laurent Koscielny were injured in Friday's 3-1 home defeat to Manchester United in the FA Cup.

While fears that Koscielny had broken his jaw in an accidental clash with Romelu Lukaku proved unfounded, the diagnosis on Sokratis will come as a significant blow with Hector Bellerin and Rob Holding already sidelined.

Manager Unai Emery had initially expressed optimism that Sokratis' injury was not serious after he was replaced 21 minutes into the fourth-round match having appeared to twist his ankle.

But a medical update on Sunday said the Greece defender was not expected to resume training until the end of February.

Koscielny's injuries, which amount to some bruising and soft tissue damage, are being assessed on a daily basis.

Earlier this week Arsenal announced Bellerin faces up to nine months out with a ruptured anterior cruciate ligament.

Holding is still on the road to recovery following surgery.

Midfielder Henrikh Mkhitaryan is back in training, while forward Danny Welbeck is recovering from surgery of his own.