Arsenal striker Viktor Gyokeres will undergo further tests this week amid fears he has suffered a hamstring injury.
The Sweden international was withdrawn at half-time in the Gunners' victory at Burnley on Saturday having scored the team's opener.
Speaking before the Champions League match against Slavia Prague on Tuesday night, Arsenal boss Mikel Arteta said: "I am concerned because he hasn't had many muscular issues and he needed to leave the pitch and he was feeling something.
"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.