The Argentinian winger, who completed his transfer on Wednesday will be a valuable addition to the Liverpool squad says the boss.
"We were looking for players with character and a good mentality. He has played for Argentina and Atletico Madrid and is a player with personality," said Benitez.
"He can play in three positions - on the right, left or as a second striker - and is someone with a very positive mentality, which is what we are looking for.
"He is comfortable on the ball, can pass and keep possession. He is good at getting into the box and scoring goals and a good finisher. Every year he gets five to 15 goals from the right side of midfield.
"I know he was not doing as well as he did in the past at Atletico Madrid, but he is doing really well with Argentina and wants to impress for the World Cup."