The Dutchman will officially move to Anfield from Southampton on January 1 for a world record fee of £75m.
Last season, Puel handed van Dijk the captain's armband at St. Mary's during his only season managing the south coast club.
Speaking before Leicester's clash with Liverpool on Saturday, which van Dijk won't feature in, Puel sung his former player's praises and was grateful he wouldn't have to face him on the weekend.
Puel said: "He is one of the best defenders in the world and he has all the qualities to become the best. It is fantastic for Liverpool.
"He can play in different good teams and it is a good reward for him. At the beginning of the season it was difficult for him because he wanted to join another club but now he will find his level. I am happy for him, and happy he can't play against us!
"Of course I don't know if it is the right price but for me he is a fantastic player, fantastic defender. I had him for six months and then for the last six months he was injured.
"In those first six months he made progress and developed his play. He has all the qualities. He is powerful, has pace and he is comfortable on the ball. He is tall and also has a strong character and personality."