Benitez said: "He is more mature, learning every day and his team-mates know he is one of the world's best two or three keepers.
"People say he has problems in certain areas but I think he's fantastic. He has adapted well to the English style and knows when to catch and when to punch.
"It's difficult to say how many points he is worth a season. In defence we are good but with Pepe there we are much better. His team-mates trust him."