Arsenal manager Arsene Wenger has revealed Wojciech Szczesny will miss "two to three weeks" of action with an ankle problem.
Szczesny, 22, will play no part in Sunday's clash with Manchester City, or the match at home to Chelsea on September 29.
Vito Mannone, who is yet to concede in the Premier League this season, is likely to deputise at the Etihad Stadium in the absence of the Poland international.
Szczesny has endured an injury-plagued start to the present campaign, missing league games against Sunderland, Stoke and Liverpool, as well as Tuesday's Champions League match with Montpellier.
His error against Southampton last weekend allowed David Fox to become the first player to hit the back of the net against the Gunners in the league this season.