Nacho Monreal is expected to be available, but Laurent Koscielny has been nursing a troublesome Achilles which flared up before the global break, while Calum Chambers is recovering from a groin problem.
The former Schalke 04 man has made six appearances in all competitions during the current campaign.
Eighth-placed Watford have just one win against Arsenal in eight Premier League meetings but will look to build on their decent start.
Laurent Koscielny is set to return to action for Arsenal this weekend during their match against Watford despite only having limited first team training.
'Koscielny has a definite final test tomorrow but at the moment he is not available.
If both defenders are unavailable, Wenger will have to turn to back-up options Per Mertesacker and Rob Holding to fill the void, as Calum Chambers also remains sidelined with a hip injury. "But he trained on his own and the first signs are positive, so we chose to give him a test tomorrow", he added.
"I will decide what I have to do when Koscielny has his test tomorrow".
"He didn't play in their first game and we lost him in the second - we have to cope with that now".
Alexis Sanchez will be assessed when he returns from global duty after he received "special treatment" following Chile's 3-0 defeat to Brazil.