Unai Emery says Mesut Ozil will require further tests on Monday and Tuesday before Arsenal can be sure whether they playmaker will be available to face Valencia in the Europa League semi-final first leg next week.
Ozil missed Sunday's 3-1 defeat to Leicester City with a bruise on his foot, an injury he has been playing with for some time.
The German has been in mixed form over recent weeks but when he has excelled Arsenal have been similarly impressive and Emery's chances of winning the Europa League would doubtless be improved with Ozil in his side.
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Whether that will be the case will not be clear until next week.
"He can't play today," Emery said. "We are going to wait for tomorrow [Monday] and for Tuesday [to see if he can play against Valencia.]"
Arsenal are also expected to be without Aaron Ramsey (hamstring) and Denis Suarez (groin) for that match with winning the Europa League increasingly looking like the Gunners best hope of Champions League after their third Premier League loss in a week.
Emery added: "We have a big ambition in this competition. It’s a semi-final and it's going to be difficult also. Then we play on Sunday against Brighton, and we need to win this match.
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"At the beginning of the season we knew it was going to be very difficult, and today it’s the same.
"Our confidence can go up, can go down. But the most important is to be clear in our minds and our way. Our way is to think of this semi-final and prepare for the match in the best possible way."
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