"We've lost Mustafi for about four to six weeks".
The 25-year-old Germany worldwide limped off with a first-half injury as the World Cup holders completed a 100% record in qualifying for Russian Federation 2018 by thrashing Azerbaijan 5-1 on Sunday.
The Premier League returns after yet another drab and dreary global break.
The former Schalke 04 man has made six appearances in all competitions during the current campaign.
"Koscielny has a definite final test tomorrow", Wenger added. At the moment, he's not available.
Wenger said: "Kolasinac is a minor problem, a hip problem".
Alexis Sanchez will not report back from worldwide duty with Chile until Friday, but Wenger has no concerns over the forward or Aaron Ramsey's mental state after their World Cup exits. Sanchez won't be back with us until tomorrow.
"It was a very physical game".
"We will assess Sanchez when he comes back, I watched the Brazil game and he got some special treatment in that game".
Wenger said contract talks with German global Ozil, who is in the final year of his deal, were progressing well. The fact that we didn't find agreement previous year doesn't mean he wants to leave. "It looks like if he survives the test he is capable to play". "At the present time there is no deal close for me to announce".
Arsenal could be boosted by the return of Laurent Koscielny against Watford. Arsenal are fifth on 13 points from seven games.