Arsenal expect Noni Madueke to miss six to eight weeks with the knee injury sustained in the 1-1 draw with Manchester City on Sunday.
However, the 23-year-old England winger is not believed to have suffered an anterior cruciate ligament (ACL) injury.
The summer signing from Chelsea was substituted at half-time of the Premier League match with City and has been having tests to discover the severity of the problem.
“It looks like Noni is going to be out for a few weeks, but we don’t really know yet, we will have to scan him next week again,” said Arsenal manager Mikel Arteta on Tuesday.
“He felt something at the beginning of the match and tried to carry on but it was too sore, so let’s see.”
Asked to confirm whether Madueke will be out for weeks rather than months, Arteta replied: “We hope so. Like I said, we need to scan him again to see the extent of the injury but it doesn’t look too bad.”
Arsenal face Port Vale in the third round of the Carabao Cup on Wednesday.
Earlier, sources indicated medics were waiting for the swelling to subside before making a definitive diagnosis on the injury, but it is understood that Madueke will be sidelined for a minimum of six weeks, though that timescale is thought to be the best-case scenario.
The news is a major blow to Arteta and England head coach Thomas Tuchel given Madueke’s promising start to the season.
If the initial prognosis is confirmed, Madueke will not return to action until November at the earliest, ruling him out of a clutch of key domestic and European games for the Gunners.
The attacker is set to miss England’s forthcoming games against Wales and Latvia, while also making him a doubt for World Cup qualifiers against Serbia and Albania in mid-November.
Arsenal face Sunderland on 8 November in the Premier League. If Madueke is unavailable for that game and the international break, he could return for the north London derby versus Tottenham on 23 November.
