The Arsenal boss has admitted Sead Kolasinac is also struggling with a hip problem suffered playing for Bosnia.
It means Mustafi isn't expected to be available before the November global break and will therefore miss Arsenal's next seven games including Premier League fixtures against Watford, Everton, Swansea and Manchester City.
"Kolasinac is a minor problem, a hip problem". But he trained on his own and the first signs are positive.
LONDON, ENGLAND - MAY 27: Per Mertesacker of Arsenal and Arsene Wenger, Manager of Arsenal speak prior to The Emirates FA Cup Final between Arsenal and Chelsea at Wembley Stadium on May 27, 2017 in London, England. For Arsenal, they face a tricky trip to Watford to face a deceptively risky side who are well-drilled, industrious, and fit under the tutelage of Marco Silva.
Amazon Oasis: Introducing the first waterproof Kindle e-reader
It will also make your device work much better and the Audible feature works on both Bluetooth headphones as well as on speakers. The regular model is Wi-Fi only and packs 8GB storage, whereas the mid-tier version has 32GB internal memory and costs $280.
Hotel worker warned of shooter before Las Vegas massacre
MGM Resorts International spokeswoman Debra DeShong said the company believes "what is now being expressed may not be accurate".
Chris Foerster resigns from Dolphins over cocaine video
Former Dolphins coach Chris Foerster was seen snorting a white powdery substance in a video. After snorting two lines, he says, "It's gonna be a while before we can do this again".
Wenger added: "The player I expected to lose the least during the break was Mustafi".
"It's always hard. The player I expected to lose the least during the break was Mustafi, because first of all I was not sure if he would play and secondly Germany were already qualified so you didn't expect him to be out injured because the games would be less intense".
'I didn't expect him to play and Germany had already qualified.
Koscielny has had the problem for many seasons and though he has not yet resumed full training, he is set to return to action with the squad ahead of Saturday's game.
Alexis Sanchez will be assessed when he returns from global duty after he received "special treatment" following Chile's 3-0 defeat to Brazil.