The French defender has been suffering with the flu in recent days and will be assessed in the build-up to the clash against the Black Cats in north London.
Speaking at a news conference on Tuesday morning, Wenger also revealed that defender Mathieu Debuchy is not yet back in full training with the Gunners as he continues to recover from a hamstring problem.
Wenger also confirmed that Alex Oxlade Chamberlain (groin) and Danny Welbeck (knee) are progressing well but will not be ready for the visit of the Black Cats.
Wenger told a news conference on Tuesday morning: “We have an uncertainty about Koscielny. He has the flu. Debuchy is not in full training yet.
“Oxlade-Chamberlain and Welbeck are progressing well but will not be available for tomorrow.”
Arsenal head into Wednesday’s clash knowing that a draw will guarantee them a top-three finish in the Premier League and a direct route into the group stage of next season’s Champions League.
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