The Spanish ace played despite an ankle problem and became the fastest player in Liverpool history to record 50 league goals.
Benitez told liverpoolfc.tv: "He had some problems with his ankle more than his groin. He's working hard with the physios and fitness coach. It depends on how he feels but he was okay for this game.
"We signed a very good player, a player with a good mentality and quality. You saw here that he has one chance and he scores.
"He is one of the best strikers in the world. For me, you can never, ever say someone is the best because there are other good strikers in other countries.
"If these players are fit and playing well then we know we're a very good team. Hopefully Fernando will be fit until the end of the season."