"Lucas is a fantastic player and a fantastic professional. He was the captain of his team when he was 19 years old, he has caps with Brazil, not with any other country - Brazil," Benitez told the club's official website.
"He was the captain of the Under-21 Olympic team for Brazil, again I will say - Brazil - and has a very, very good mentality.
"When you talk about Brazilian players, OK you can say they are maybe skilful players with ability, but Lucas is a worker, he has quality and has a very good approach for each game.
"He can tackle, he can win the ball in the air and he can pass well.
"But he is still a young player in a different country and he is competing against Javier Mascherano, the captain of Argentina, Steven Gerrard, one of the best players in the world who has captained England and Xabi Alonso, one of the best players in the Spain side, the champions of Europe.
"I think it is difficult for a young player to compete with them, but that just shows the amount of quality in our midfield.
"If you analyse how Lucas was playing before, and how he is playing now, he was working so hard in the last few matches but people were disappointed with him.
"He is the kind of player who has a very good character and I'm sure he will be a very good player for us in the future."