Arsenal manager Arsene Wenger has confirmed goalkeeper Petr Cech is set to miss up to four weeks with a calf injury.
The Gunners slumped to a 2-1 defeat at home to Swansea City on Wednesday to leave them six points off Premier League leaders Leicester City in third place.
But Arsenal's faltering title bid suffered another blow when Cech injured his calf running back to his goal after going up for an injury-time corner as Wenger's men sought a late equaliser at Emirates Stadium.
Wenger said Cech had already been in some discomfort following Swansea's equaliser and the goalkeeper is now set for a spell on the sidelines during a crucial period.
"Cech is out," Wenger told a news conference ahead of Saturday's north London derby against title rivals Tottenham.
"It is three to four weeks for Cech. It's not more serious than first thought. He had a groin [problem] on the first goal. He couldn't kick the ball properly."
The French manager insisted he has no concerns about the ability of back-up goalkeeper David Ospina, adding: "I have complete confidence in Ospina and I'm not worried at all on that front."
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