Gerrard has been struggling with a niggling groin problem that has seen him play just 25 minutes of Liverpool’s last five games.
“He has lost part of his fitness and we will see if he can play against Birmingham or be on the bench, but we know he will not be fully fit and maybe he will be out,” said Benitez.
“When a player has not trained with the team for 15 days he cannot be 100 per cent fit. Is he available? We will see. They are two different things.”
Spanish striker Fernando Torres is also struggling with a groin problem, but Benitez could decide to throw him into action against Birmingham on Monay.
He added: “It’s our decision if he plays against Birmingham or not. He is feeling better than he was before so he can carry on with the pain.
“It’s not a problem. It’s a question of whether he’ll be fully fit or not, but the decision is not a risk.
“If we decide to play him it’s because it will be good for the team and not a big problem for the player. We know 100 per cent it’s not a problem.”
