The goalkeeper suffered an injury blow during the Gunners’ 5-1 win over Everton and had to be replaced by David Ospina.
With two days until the clash at Wembley, Wenger admits Cech is unlikely to fully recover in time.
Danny Welbeck and Naco Montreal, though, are both set to be available, with the latter having been substituted against Everton too due to illness.
“We should have a similar squad to Everton,” Wenger said. “Maybe Welbeck will be back.
“We are not sure with Cech, he has not practised. I don’t know if he should be available.
“Nacho Monreal should be alright.”