The Sun says the Spanish striker is battling a damaged groin and surgery could KO him for two months.
Steven Gerrard might also go under the knife on Thursday if a scan on his groin confirms the worst.
But he said: "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."