Arsenal captain Martin Odegaard is set to be sidelined for a "few weeks" with a knee injury.
Odegaard sustained a medial collateral ligament injury during the 2-0 win over West Ham before the international break, leading him to withdraw from international duty for Norway.
Arsenal boss Mikel Arteta said on Friday: "He will be weeks, no definite date for his return, but he's evolving well. It's very unlucky what's happening with him and his injuries this season, but I think he will be back in a few weeks.
"It could be [an absence until after the international break] but we will have to see how he is progressing, how his knee is feeling, how he manages the next steps in his rehab, it's too early to get an answer."
It is the third injury blow Odegaard has suffered this season following two issues with his shoulder which forced him off early against Leeds in August before later missing three matches the next month.
Fresh Odegaard injury will test Arteta
Analysis by Sky Sports' Laura Hunter:
Arsenal might be top of the Premier League, but they have taken some considerable blows across the first part of this season. Recurring injuries are becoming a running theme.
Of course there are two sides of this coin. Mikel Arteta will point to how well his squad have coped with notable absentees. And he would be right to.
Arsenal now have a group capable of keeping pace with the best when Martin Odegaard, Bukayo Saka and William Saliba, among others, have been missing - that could not be said of last season.
But the slog has, really, only just begun. To have sustained so many injuries to key players this early on is a concern. Chiefly, the loss of Odegaard to a different problem will be tough for Arteta to take.
I was at Arsenal's win over West Ham a fortnight ago, when Arteta had the bravery to try Odegaard and Eberechi Eze in the same system, only for the Gunners captain to limp off after 30 minutes. The clash with Crysencio Summerville - knee on knee - looked innocuous enough but clearly did damage.
The average time lost to an MCL injury is 41 days. It can be longer. The presence of Eze will soften the blow, with Ethan Nwaneri or even Mikel Merino also able to step in, but this is far from perfect news in terms of balancing fixtures across multiple competitions.
In the meantime, the true depth of this Arsenal outfit will be put to the test, as will Arteta's management of a squad thought to be the strongest he's ever worked with. He certainly cannot afford any further setbacks.
Arsenal's next five fixtures
Fulham (A) - Premier League - Saturday October 18, live on Sky Sports
Atletico Madrid (H) - Champions League - Tuesday October 21
Crystal Palace (H) - Premier League - Sunday October 26, live on Sky Sports
Brighton (H) - Carabao Cup fourth round - Wednesday October 29, live on Sky Sports
Burnley (A) - Premier League - Saturday November 1