Arsene Wenger has confirmed Arsenal defender Shkodran Mustafi could miss up to six weeks with a hamstring injury.
The centre-back picked up the injury in Germany's 5-1 victory over Azerbaijan on Sunday, when he was forced off after 36 minutes.
Wenger also revealed Sead Kolasinac, who was taken after 45 minutes of Bosnia and Herzegovina's 2-1 win over Estonia on Tuesday, is a doubt for Saturday's visit to Watford with a hip injury.
"I haven't seen everybody because some players are coming back today, some even tomorrow like Alexis Sanchez," Wenger said on Thursday, when questioned about injuries picked up during the international break.
"The minor problem we have is with Sead Kolasinac. We will check him today. He has a hip problem.
"We lost Mustafi for about four to six weeks. I don't think he will be available before the next international break.
"[Mesut] Ozil and [Danny] Welbeck are back in the group in normal training."
Arsenal could be boosted by the return of Laurent Koscielny against Watford.
The France international has been dealing with an Achilles injury and missed Les Bleus' recent victories over Bulgaria and Belarus.
Wenger explained: "Koscielny has a definite final test tomorrow. At the moment he is not available. But he trained on his own and the first signs are positive so we decided to give him a test tomorrow."