Mesut Ozil is set to miss Arsenal's game at Liverpool on Saturday after being left out of the travelling squad.
Ozil was pictured in training on Friday but was not with the squad when they arrived at their Liverpool hotel in the evening.
Club officials would not confirm Ozil's absence when contacted by ESPN FC, but it has been reported that Ozil complained of knee pain after the training session and was withdrawn from the matchday squad.
Ozil's absence comes after he has been in and out of coach Unai Emery's team, having been benched for two recent away matches and missing nearly two weeks with a back problem.
He started at Brighton on Wednesday, only to be taken off at halftime for what Emery insisted were "only tactical" reasons.
Emery was already without attacking midfielder Henrikh Mkhitaryan, who has a broken metatarsal, and now enters the game against the league leaders with limited attacking options and a number of defensive injuries.
Right-back Hector Bellerin is out, while centre-back Shkodran Mustafi could be in line for a return after struggling with a hamstring injury.