Arsenal boss Arsene Wenger has revealed that Petr Cech will be out of action for a month after sustaining an injury in his side's 2-1 loss to Swansea in midweek.
Cech, who will definitely miss the North London derby against Tottenham Hotspur, injured himself in the final minutes of the game against Swansea.
The goalkeeper will also miss the Champions League round of 16 clash with Barcelona billed for 16 March.
He now joins the likes of Jack Willshere, Santi Cazorla, Tomaz Rosicky and skipper Mikel Arteta on the sideline.
In his press conference ahead of Saturday's lunch-time kick-off, Wenger also ruled out Laurent Koscielny from the game.
"Petr Cech is out Koscielny is not back. Cech will be three or four weeks with a calf injury," Wenger said.
"Koscielny has a small injury and will be out for tomorrow."
Wenger however expressed confidence in the ability of second choice David Ospina.
"I have complete trust in Ospina, I don't worry about that."
Speaking ahead of the clash against Spurs, Wenger described it as a title decider.
He added: "It is a big one, a very important one. The preparation is the same."
"We have a competitive rivalry but a fair one. You have that in all sports.
"It is hard to predict what will happen tomorrow. It is one of the few derbies where the title is at stake."