Arsenal manager Arsene Wenger says he is "concerned" over Arsenal's defensive woes ahead of Saturday's trip to Watford, with two of his three three first-choice centre halves potentially missing from the teatime clash.

Laurent Koscielny faces a race against time to be fit for the game at Vicarage Road, with Sead Kolasinac also a doubt and Shkordan Mustafi ruled out for up to six weeks.

As reported earlier this week, the trio could leave Wenger fielding an untested backline of Per Mertesacker, Rob Holding and Nacho Monreal, a backline which has not been tested this season.

Should Koscielny and Kolasinac miss out, it would give added belief to the Hornets' front line, who have scored 11 goals already this season - as many as the Gunners.

And even if the Frenchman is fit, he has not trained with his team-mates for almost a fortnight, so will have some rust to shake off if he does start.

Wenger said: “I have concern. I will decide tomorrow what I will do.

“Koscielny has his test tomorrow - If he survives the test he will play. But he trained on his own and the signs are positive so he has a test tomorrow."

The Gunners boss confirmed Mesut Ozil and Danny Welbeck have returned to training at London Colney, although neither is expected to start Saturday's match without having had the chance to pick up sufficient game time.

In his pre-match press conference, Wenger was also - briefly - asked about Watford's impressive start to the season, and said: "Marco Silva has impressed. He has done very well."