Fernando Torres is reportedly suffering from a hernia problem that will need surgery if he is overplayed.
The Times claims the Liverpool medical staff have told Benitez that the Spanish striker needs to be treated with kid gloves or he will need an operation that will rule him out for two months.
The inguinal hernia apparently developed while he was on international duty in October and the striker has been playing in pain and rationing his training ever since.
He was withdrawn after an hour against Fulham at the weekend and will start against Lyon on Wednesday night.
Benitez admitted: "We are trying to manage, as he was close to having an operation. Two days after the Fulham game, he is still feeling something.
"He is not comfortable and hasn't got the power he had before, so we have to try to protect him.
"Fernando cannot play well if you keep pushing him. Maybe if you push him he will be injured for a long time."
Steven Gerrard has been ruled out of the crunch game against the French side with a groin injury - which could need surgery - along with Martin Skrtel.
Alberto Aquilani has been added to the squad despite still being "weak" from a virus that kept him out of the game with the Cottagers, while Daniel Agger and David Ngog will travel despite carrying slight knocks.