Laurent Koscielny is struggling to be fit for Arsenal's clash with Manchester United on Sunday.
Koscielny is set to miss Sunday's crunch Barclays Premier League clash against Manchester United after picking up a hamstring strain against Olympiakos, says the Daily Mail.
The Frenchman is undergoing tests to determine the extent of the damage; nevertheless his likely absence for the visit of the current league leaders comes as a major blow to Arsene Wenger ahead of the clash against United - as well as his plans to implement a new combination in central defence.
Wenger and his backroom staff have been impressed by Gabriel's performances during Per Mertesacker's absence from a chest infection.