Arsenal are assessing striker Kai Havertz after he suffered a muscle injury on the team's Dubai training camp.
There are fears that the 25-year-old has torn his hamstring and could miss the rest of the season.
The Athletic have reported that it is unclear if he will need surgery but report that his season is likely to be over, external.
The German has made 34 appearances across all competitions this season and is the club's top scorer with 15 goals and five assists.
Manager Mikel Arteta will be asked about the extent of the injury at Friday's news conference before his side take on Leicester City on Saturday.