Benitez said: "Gerrard is definitely out tomorrow. He has a thigh muscle problem and won't be playing.
"We might make other changes as well. Maybe we'll leave another key player out. It depends on the positions. Sometimes you have two players challenging for one place and that makes it easier to switch them from game to game.
"We know that fourth place is impossible now but I want the players to give a good performance on Sunday. We want to end with a win for our fans before we go and play the final.
"I'm not thinking a lot about the final at the moment. My idea is to look at the next game because I know we'll have more than a week to prepare properly for Istanbul."