Arsenal manager Arsene Wenger has confirmed that attacking midfielder Alex Oxlade-Chamberlain is expected to be on the sidelines for weeks.
The Englishman suffered a knee injury during the mid-week Champions League defeat against Barcelona.
He joins the likes of Jack Wilshere and Tomas Rosicky on the sidelines but Gabriel Paulista will be assessed tomorrow morning to understand if he can face Manchester United on Sunday.
"Gabriel [Paulista] has a test today and tomorrow then we will see if he is available for the game," Wenger said.
"We lost [Alex] Oxlade-Chamberlain on Tuesday night.
"It's not [a recurrence of a previous injury]. Not at all. It's a new injury. He has been cut in two by Mascherano and he did his knee. We have to see how big the damage is in his knee.
"He is consulting a specialist at the moment. Hopefully we will have good news. How long is he out for exactly? I don't know.
"He [Danny Welbeck] has been out for a while, we still need to be cautious with him.
"He is back in the squad but we still have to be cautious with him. He is still in the squad and he is not completely over his knee problem. He has done really well and is very fit. I have to analyse that.
"He [Jack Wilshere] is not back in full training yet."