The Spanish superstar said: "Robbie really wanted to come to us and you can already see he is going to bring us an enormous amount - hard work, goals and experience.
"He will bring the level of the team up a notch.
"Keane has a proven record and great mobility and versatility. He can play on the wing or a bit behind the striker.
"It is very good for the team to have a player who can get in between the opposition's midfield and defence and score goals.
"The tactical lay-out of the team, and whether or not we are going to play two up front, is down to Rafa Benitez.
"When he signed Keane I'm sure he had a very clear idea of where he wanted to play him.
"But he is very adaptable. He could fill a number of different roles."