Despite some reservations about his £75m price when he first made the move, the Dutch international has since gone on to establish himself as one of the best defenders in the world.
"He brings everything, in my opinion," Robertson said of the No.4. "He is one of the leaders in the changing room now, he is vocal.
"He is a lovely person off the pitch. He has been so crucial to what we do.
"The players around him have helped; Joel [Matip] has been magnificent when he has been called upon this season, Joe Gomez was different class at the start of the season, and Dejan [Lovren] has obviously played games and stepped up where he has been great.
"The central partnerships have been really good this season. Virgil takes all the plaudits but rightly so – he has been on a different level to anyone this season. What he brings on and off the pitch is special."