Arsenal expect Noni Madueke to miss about 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 international is not believed to have suffered an anterior cruciate ligament injury.
The summer signing from Chelsea was substituted at half-time of the Premier League match with City and has been undergoing tests to discover the severity of the problem.
Sources are indicating medics are 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.