Benitez said: "People just don't know how good Lucas is. He is a fantastic player, he was captain of his club side at 19 and has already won full caps with Brazil.
"Not just any country, but Brazil. He has captained their Under-21s and their Olympic team. He has a very good mentality. When you talk of Brazilian players you know they are skilful with ability. But Lucas is a worker and has a very good approach.
"He can tackle, he can pass the ball and he can win in the air. He is still a very young player learning to live in a different country. It is not easy for him to get into the team, considering the quality of the opposition he has to face in that department at Anfield.
"He is competing against Javier Mascherano, the captain of Argentina and against one of the best players in the world, Steven Gerrard, who has also captained his country. And then there is Xabi Alonso, who is now a European champion for club and country.
"That shows how difficult it is for a young player to compete with them, and it shows the quality in our midfield."