Arsenal could be forced to sign a centre-back in the January transfer window amid the club's defensive shortage, head coach Unai Emery admitted.

Emery's options in defence are limited after Arsenal centre-back Rob Holding suffered a season-ending knee injury last week, while veteran Laurent Koscielny is only set to make his first appearance since May in the Europa League against Qarabag on Thursday.

Key duo Sokratis Papastathopoulos and Shkodran Mustafi are suspended for Sunday's trip to Premier League strugglers Southampton, and Konstantinos Mavropanos has not played all season due to a groin injury.

Discussing the potential need for reinforcements, Emery told reporters: "If we can take one player to help us at centre-back, I think it's a good option. But a transfer is not easy."

Koscielny will make his long-awaited return in the Europa League after a ruptured Achilles robbed him of a place in France's World Cup-winning campaign.

An accumulation of yellow cards following the Premier League win over Huddersfield Town mean Sokratis and Mustafi are serving one-game suspensions, while Holding could be out for up to nine months due to a ruptured anterior cruciate ligament sustained against Manchester United.

Arsenal – amid a 21-match unbeaten streak in all competitions – have already qualified for the next round of the Europa League and sit fifth in the Premier League.