Aquilani is desperate to get started, but has so far been limited to a bench role.
Benitez said: "If I could change anything, it would be to have our big players fit. For a change it would be good to have a problem of who to select, before this has not been the case.
"It has been difficult with Aquilani. He has not been fit so he has no match fitness, therefore I cannot use him.
"Then if he doesn't play games, he cannot get the match fitness. That has been the difficult circle of events for him and for me to overcome.
"It was difficult again against Debrecen. Early on we could have scored two or three more goals, but towards the end we were under pressure and I could not risk bringing him on in such a situation, he would have needed time to settle.
"I have talked to him and explained. He has to keep working hard in every training session. His chance will come."