Arsenal manager Arsene Wenger has revealed that Laurent Koscielny was taken to hospital following his injury against Fenerbahce on Wednesday.
The Frenchman was taken off in the first half of their 3-0 win after being kicked in the face by Pierre Webo.
The centre-back was stitched up in the dressing room and Wenger said that Koscielny was later taken to hospital for further treatment on the bloody wound.
"Laurent Koscielny has opened very deeply the skull and we had to take him to hospital," Wenger said after the game.
"I was not happy with the kick because I feel always that you can ease a bit off. Only the player in the end will know what he did.
"We are concerned because we had to send him to hospital to see if he has not broken a bone. We are waiting for him to come back now, for information to find out if he can fly home with us."
The Gunners physio Colin Lewin told Sky Sports News that the cut was one of the worst he had ever seen and described the wound as "horrible".