Klopp is waiting for Friday's semifinal draw after victory home and away against Manchester City.
Cuba played for Klopp at Borussia Dortmund and wishes his former manager all the best.
He said, "In the end, Liverpool are in the semi-finals, so I'll keep my fingers crossed for my former coach.
"We've seen a lot of beautiful things together.
"I'll keep my fingers crossed for Kloppo!"