Wenger says the Pole needs a " breather".
"He has played many games and [been under] a lot under pressure," the manager said. "And recently, he had one or two games where he was performing less.
"With goalkeepers it's always a difficult problem. Do you keep them in to find confidence back or do you give them a breather?
"I decided to give him a breather just to refresh him and [so that he would] not be under increasing pressure, because once people start speaking about you, you think, 'Now I cannot afford any [errors]' and that's when you make mistakes."