The goalkeeper suffered the problem late on during the 2-1 loss to Swansea City in the Premier League on Wednesday night and will miss Saturday’s trip to Tottenham Hotspur.
Wenger also confirmed that Laurent Koscielny will definitely miss Saturday’s clash at White Hart Lane due to a minor muscular problem but could return for next weekend’s game.
Speaking at his pre-match news conference on Friday morning, Wenger said: “Petr Cech is out and Laurent Koscielny is not back.
“We have a check this morning that everybody is available for tomorrow who played on Wednesday night.
“[Cech will be out] three to four weeks. It’s serious calf injury. He had groin alert and maybe provoked another muscular injury.
“Yes, it is a loss but on the other hand if you look at the win-rate of Ospina, it is very good as well.
“Koscielny has a small injury but is out for tomorrow. Next Saturday he should be alright.”
Meanwhile, the Arsenal boss also revealed that midfielder Jack Wilshere is around three to four weeks away from returning to action for the north London side.
He added: “Wilshere is going on plan but is still three to four weeks [away] for him.”
Arsenal head into Saturday’s game knowing that a win would move them level on points with Tottenham in the Premier League table.
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