The Swedish forward missed training on Monday after being substituted with the issue during Saturday's 2-0 win over Burnley.

Arteta confirmed he will definitely miss Tuesday night's Champions League match against Slavia Prague but indicated there was uncertainty over just how bad the problem was.

"I am concerned because he hasn't had many muscular issues and he had to leave the pitch and he was feeling something," Arteta said on Monday evening.

"That's obviously never a good sign, especially for a player that is very, very explosive. So we are digging in a little bit more to understand where we are in terms of the injury and we'll announce the moment we know.

"He's definitely not available (to play Slavia). He hasn't trained today. We need to do some more tests and scans in the next few days to understand the extent of the injury."