Petr Cech pulled up at the end of tonight's match with Swansea
Wenger was speaking after the Gunner's title hopes suffered a heavy blow as Swansea came from a goal behind to win 2-1 at the Emirates.
Cech was injured at the end of the game when he pulled up short as he ran up for a corner as the Gunners chased the game.
The Frenchman said: "Cech got a muscular problem at the end of the game. He will not play on Saturday. I have full faith in Ospina"
Koscielny missed tonight's match after suffering a slight calf problem, and Wenger confirmed he would also miss the north London derby on this weekend.
Arsenal's defeat to Swansea dealt the Gunners a huge blow in the race for the title, and Wenger insisted his side were unlucky to lose the match.
He said: “The performance was okay, but we were unlucky on the night. We were on top and hit the bar a number of times. We were unlucky on the first goal. There was a foul on Ozil; we stopped playing and they took advantage of that.
“I still don’t understand why it was not given a foul. We were really unlucky. What we want is to win the next game."
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