Granit Xhaka has been ruled out of the clash with Manchester United this weekend.
The Swiss midfielder suffered a knock to his ankle in the north London derby defeat to Tottenham last week and hasn't recovered sufficiently to feature when Arsenal welcome Jose Mourinho's men to the Emirates.
Elsewhere, Shkodran Mustafi is back training after missing the derby through injury but Lucas Perez will miss out.
"Granit Xhaka is still out. (Shkodran) Mustafi is back in normal training, that’s basically it," he said in his pre-match press conference ahead of Sunday's match.
(David) Ospina is fully fit, Lucas Perez is back in training but will miss the next couple of days after picking up a knock."
With the second-leg of the semi-final with Celta scheduled for just four days after Sunday's game Mourinho has said he'll rest his key players where necessary at the Emirates.
But Wenger is sure whatever team the Portuguese selects it'll be a strong one.
"We focus on our performance," he said when asked about Mourinho's comments. "I don’t know what Man Utd will do. We know anyway they have a massive squad with quality players and only a top performance will get us the win we want.
"The only advantage we can give is to focus on ourselves not a weaker Manchester United. No matter who plays they will have a strong team out.
"What I want is that my team turns up with a strong performance on Sunday."