Klopp admits he was a fan of the Portugal international when he was captain of Sporting CP.
Ahead of Sunday's visit of United, Klopp stated: "He's a brilliant player. We played against Sporting Lisbon in a training match in the USA before he came to United, and even then we could see it… Wow! He is a player who makes a difference, and he is showing that now.
"You can talk about all his goals scored, but he sets up other players as well. Without knowing him personally, he appears to be a leader.
"A good signing, unfortunately, for Manchester United..."