London - Arsenal's hopes of capturing their first Premier League title in 12 years took a huge hit on Friday with news that goalkeeper Petr Cech faces up to a month out injured.
The Czech Republic international suffered a muscular problem at the end of Wednesday's 2-1 loss at Swansea City.
That reverse left the Gunners six points below Premier League leaders Leicester City in third place, ahead of Saturday's trip to second-placed Tottenham Hotspur.
Cech's absence confirmed by manager Arsene Wenger at a press conference on Friday thrusts Colombian World Cup goalkeeper David Ospina into the spotlight.
"(He will be out for) three to four weeks," the Frenchman said.
"It is not more serious. It is a serious calf injury and he had a groin alert on the first goal and he could not kick the ball properly out because of his groin and maybe compensated a little too much and provoked another muscular injury."
Former Chelsea star Cech injured his calf as he raced back towards his own penalty area after coming up for a corner against Swansea.
Wenger revealed that Cech had a groin issue before the game but trusted him to play only to see his first-choice goalkeeper pick up a different injury.
The same happened with Alexis Sanchez earlier in the season when Wenger played him against Norwich despite knowing of a hamstring problem which then flared up in the game and ruled him out for the festive period.
"We had to make the decision before the game because he had a little groin problem but he declared himself 100 per cent fit," he said.
"Then you have to trust the player. He's 33 years old and he knows his body. If he says he's fit then he is available.
"It is like it is. I focus on the future. You want the players to be tough enough to sometimes be able to play through a little pain. You're never completely perfect before a game in March."
Ospina will deputise for Cech at Spurs and in the coming weeks - with an FA Cup replay at Hull and a Champions League tie in Barcelona to come as well as league games against Everton and Watford.
The Colombia international came in for criticism after a howler in the Champions League defeat to Olympiakos earlier this season but Wenger has backed his man to step up now he is needed.
"I have complete confidence in David and I'm not worried at all on that front," he added.
"If you look at the win-rate of Ospina it is very good as well. I'm not worried at all on that front."