Petr Cech will miss the North London derby.
Goalkeeper Petr Cech picked up a hamstring injury late on, and will miss the upcoming fixture against Tottenham Hotspur on Saturday.
David Ospina will take his place, with Wenger talking up the Colombian international.
Wenger: "Cech got a muscular problem at the end of the game. He will not play on Saturday. I have full faith in Ospina." #AFCvSCFC— Arsenal FC (@Arsenal) March 2, 2016
Cech was injured in most unfortunate circumstances. He had gone up for a corner to try and score an unlikely equaliser, and pulled his hamstring running back to his own end.
The defeat really was a costly one for the Gunners, who have now won only four of their last 11 matches.
The 2-1 loss at home to Swansea City leaves them six points behind leaders Leicester. Tottenham lost to West Ham, meaning Arsenal could draw level on points with their rivals at the weekend with a win.