Arsenal manager Arsene Wenger says midfielder Francis Coquelin will not be in the squad to face Tottenham Hotspur on Wednesday night.
The Frenchman will be assessed in the coming days ahead of Saturday's Premier League game against Leicester City.
Defender Per Mertesacker returns after illness and will be a regular against Spurs.
"Francis Coquelin will be out and we have no major problems for anybody else. It should be a similar squad," Wenger said on Tuesday.
"His knee is swollen and he is being assessed but we hope it is just a short-term problem.
"He [Per Mertesacker] is available for selection, yes.
"Alex Iwobi [could feature]. He is in and out a little bit because we travel a lot. He is doing well.
"I want to keep the squad together. We go game by game so I will make changes, for sure. How many? I've not decided yet. It will be quite an experienced squad with one or two younger players."