Martin Ødegaard's early season injury woes continued on Saturday when he was forced off in the 18th minute of Arsenal's 3-0 win over Nottingham Forest.
Ødegaard's frustration will be compounded by the fact his injury was prompted by a collision with his own teammate at the Emirates.
The Arsenal captain fell awkwardly after Jurriën Timber inadvertently made contact with Ødegaard while attempting to win the ball from Forest's Morgan Gibbs-White on the edge of the penalty area.
Ødegaard left the pitch holding his shoulder -- an injury he first suffered during Arsenal's win over Leeds United on Aug. 23. The shoulder issue also meant he was not included in Arsenal's starting XI for the 1-0 defeat at Anfield before the international break.
He was replaced by Ethan Nwaneri.
Speaking after the match, Arsenal boss Mikel Arteta confirmed the injury was "very similar" to the shoulder issues that have bugged Ødegaard of late but sounded optimistic that the player might be in line to feature in the team's Champions League opener in Bilbao against Athletic Club in midweek.
"Yes,Very similar. I don't know if it is exactly the same place but it is a very similar injury. He wasn't comfortable to continue," Arteta told a news conference.
"He has played two games with Norway and unfortunately he cannot carry on today so we have to assess him with the doctors and see. But I'm sure he will try his best to be fit for Tuesday."
Asked if there was a chance that Ødegaard could require surgery, Arteta said: "I'm not the expert but they weren't concerned at that level at all. The last time in a few days he was able to manage the pain, especially as the injury wasn't that bad. I don't know the extent of today's but hopefully not."
Arsenal were able to brush off the loss of their captain as two goals from summer midfield addition Martín Zubimendi and forward Viktor Gyökeres condemned Ange Postecoglou to a losing start to his time in charge at Forest.
Mikel Arteta has been frustrated by repeated injuries to some of his key players last season and in the early stages of this campaign.
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Bukayo Saka is still working his way back to fitness, but the hamstring injury he picked up against Leeds turned out to be not as serious as first feared.
Gabriel Jesus, Kai Havertz and Christian Nørgaard are also unavailable to the Arsenal manager as they rehab injuries of their own.
Information from ESPN's James Olley contributed to this report.