Koscielny's likelihood of playing is rated at 30 per cent by Arsene Wenger while Ozil is close to recovering from a knee problem and will be assessed.
Sead Kolasinac, however, will be out for two weeks after taking a knock to his ankle against West Brom on Sunday.
Elsewhere, Aaron Ramsey and Olivier Giroud both have hamstring injuries and remain on the sidelines, as does Nacho Monreal, who has an ankle problem.
The Gunners dropped to sixth place in the Premier League on Tuesday night after Tottenham beat Swansea 2-0, but have the chance get back above their arch rivals if they can overcome Chelsea tonight.
Arsenal (from): Cech, Ospina, Mertesacker, Holding, Mustafi, Koscielny, Chambers, Debuchy, Bellerin, Nelson, Maitland-Niles, Coquelin, Wilshere, Xhaka, Elneny, Ozil, Iwobi, Sanchez, Welbeck, Walcott, Lacazette.