"I don't think he will be available before the next worldwide break (in November)", Wenger told a news conference on Thursday.
The Gunners's fine form was interrupted by the worldwide break, which saw a number of Arsenal players qualify for next year's World Cup.
However, while the teams are closely matched from an historical perspective, Arsenal have dominated recent games with the Gunners gaining success in eight of the last 10 matches.
Arsenal extended their unbeaten run to seven matches last time out, comfortably beating Brighton 2-0 at the Emirates.
Wenger said in a press conference: "We lost Mustafi for four to six weeks".
Both sides have a number of injuries heading into the game, but Arsenal's squad depth could be a major deciding factor.
Their winning run on the road came to an end when they drew at West Brom, but the story of that came tells a very different story to the result as they managed to come from two goals down against one of the league's most stingy defences, and they eventually ended up dominating before Richarlison's late header gave them a point.
The 20-year-old Hornets wide-man has been an instant hit since being introduced to the Watford faithful, providing the team with three goals and an assist since his move from Fluminense.
Midfielders Nathaniel Chalobah and Isaac Success are also sidelined with similar injuries (knee), while Andre Carrillo will be assessed after his return from global duty with Peru.
Laurent Koscielny has been another injury worry of late with a recurrent Achilles problem, and Wenger confirmed that the centre-back will have a late fitness test, have recently stepped up individual training.
The Gunners are hopeful that Sead Kolasinac will be okay despite being forced off at half time for Bosnia on Tuesday. Shkodran Mustafi became the first new addition to the treatment table after picking up a thigh problem while playing for Germany, a setback that is expected to keep him out for six weeks.
Francis Coquelin could be back in contention after recovering from a hamstring issue but Calum Chambers and Santi Cazorla remain unavailable.