By Arsenal correspondent Tony Hughes

Petr Cech will be sidelined for a month with a calf injury in a shattering blow to Arsenal’s title hopes.

Arsene Wenger revealed at his media briefing on Friday morning that the goalkeeper will be out for “three to four weeks” with the injury sustained in Wednesday’s 2-1 defeat to Swansea.

However, Laurent Koscielny’s calf injury is not as serious and he should be back next week after missing the Swansea clash.

“Cech will be three or four weeks with a calf injury,” said Wenger. “Koscielny has a small injury and will be out for tomorrow.”

Both players will be absent for Saturday’s north London derby showdown at White Hart Lane as Arsenal attempt to get their title challenge back on track following consecutive Premier League defeats.

Cech, who has had an outstanding debut season at Emirates Stadium, will be replaced by his deputy David Ospina.

“I have complete confidence in Ospina, I don’t worry about that,” said Wenger.

Speaking on Wednesday, Wenger explained why Cech was not at his best as Arsenal slumped to a third consecutive defeat for the first time since April 2010.

“He struggled,” Wenger said at his post-match media conference. “He had a little groin problem before the game and I think he struggled a little bit tonight.

“He will not play on Saturday. I don’t know how serious it is, we have to see. It’s a muscular problem, a calf problem and I don’t know how long he will be out for. I trust Ospina completely.”

Arsenal’s hopes of landing a first league title in 12 years suffered a heavy blow as Swansea came from behind to win at Emirates Stadium.

In other Arsenal injury news, Santi Cazorla has revealed that he hopes to be back playing within a month.