Hal Robson-Kanu of West Bromwich Albion and Shkodran Mustafi of Arsenal battle for the ball during the Premier League match between Arsenal and West Bromwich Albion at Emirates Stadium on September 25, 2017 in London, England.
There is better injury news, however, regarding Sead Kolasinac, who was forced off whilst playing for Bosnia on Tuesday night with the left-sided defender expected to be available for the game against the Hornets.
Wenger gave a prognosis of four to six weeks, meaning that Mustafi could return after the next global break, but the Gunners boss will be keen to ensure that Mustafi is available for the Christmas period.
Wenger will have Mesut Ozil and Danny Welbeck back in contention against Watford, with the duo having resumed full training following respective knee and groin injuries.
"The minor problem we have with Sead Kolasnic, we'll check him today, it's a hip problem", the Frenchman said on Thursday.
"Not all the players are back".
"We will assess Sanchez when he comes back, I watched the Brazil game and he got some special treatment in that game".
"Koscielny has a definite final test tomorrow". He trained on his own and the first signs are positive.