Laurent Koscielny is likely to miss Arsenal's clash with Manchester United, report The Telegraph.
The French international suffered an injury in the Champions League defeat at home to Olympiakos, and is not expected to recover in time for Sunday's clash at The Emirates.
It is claimed by The Telegraph that Koscielny has a torn hamstring, and will also miss France's upcoming international friendlies.
The game against United will be the second big game this season Kosicelny has missed, having sat out the home game against Liverpool with back trouble.
Fortunately for Arsenal they kept a clean sheet in that clash, but that was largely thanks to heroics from Petr Cech and a slice of luck from the woodwork.
The Telegraph report Petr Cech is expected to play, after being surprisingly left out of their game in midweek.
Koscielny's injury does illustrate that Arsenal are light at centre-back, for had Gabriel Paulista been subject to a lengthier suspension after the Chelsea game, Per Mertesacker would be the club's only senior centre-back.
With United's attack taking on a new dimension with the signing of Anthony Martial, Arsenal will need to try and position the more athletic Gabriel up against him, so not to leave Mertesacker's lack of pace exposed.