Mesut Ozil and Kieran Tierney have not been pictured with the Arsenal squad at the team hotel ahead of the clash against Manchester United.
There were 18 players pictured together at the team hotel, including Rob Holding, who is hoping to make a return to the Premier League after nine months out with ruptured knee ligaments.
Hector Bellerin, as expected, has not travelled with the team. He featured in the Gunners' Under-23 side at the weekend as he continues his own comeback from knee surgery.
But Tierney's absence from the squad would be something of a surprise, following his return to action against Nottingham Forest in the Carabao Cup. The former Celtic star was in the starting line up for the 5-0 win.
Meanwhile, Ozil's future looks to be far from certain, with rumours that the club are considering a loan for the German star in January.
He again misses out on an Arsenal squad following absences against Aston Villa and Eintracht Frankfurt in recent weeks. He was afforded a start as Unai Emery changed things up for the Forest clash, but Ozil has slipped down the pecking order, despite being named as one of Emery's leadership group in the past week.
Ainsley Maitland-Niles could make a return after picking up a red card against Villa and seeing himself suspended for the Carabao Cup fixture, while Tierney's absence on the left would likely mean a recall for Sead Kolasinac.
Confirmed travelling squad: Bernd Leno, Emiliano Martinez; Ainsley Maitland-Niles, Rob Holding, Sokratis, David Luiz, Callum Chambers, Sead Kolasinac; Lucas Torreira, Matteo Guendouzi, Granit Xhaka, Joe Willock, Dani Ceballos; Gabriel Martinelli, Reiss Nelson, Bukayo Saka, Nicolas Pepe, Pierre-Emerick Aubameyang.
