"Ancelotti is the best coach in the world," Gennaro Gattuso told Diario AS.
"Carlo comes from three or four generations ago. And he always has the key to get inside the players' heads. Regardless of tactics or his way of training, he is the best for this. It seems easy but it is not."
Gattuso replaced Ancelotti in charge of Napoli in December 2019, after Carletto was unexpectedly sacked despite qualifying for the Champions League Round of 16.
The now-Valencia manager says it did put a strain on their relationship, forged when Ancelotti was Gattuso's boss at AC Milan.
"When I played, I was already a coach. When I see that a person gives you everything (Ancelotti), I go to the fire for him," Gattuso added.
"When he saw something that I didn't like in the locker room (at Milan) he spoke for the good of the team, not for my good. The relationship was this. Now the relationship is a bit [not what it used to be]...
"When I went to Napoli, he was the coach who left there for me to join. For a few months there was a lot of talk in the newspapers that the team was not well when Carlo was there... he was not physically well.
"In those two years some things were not done well. But I have great respect for him. I have spoken with him a year ago. He knows that for me he is phenomenal as a person and as a coach."
Ancelotti's Real Madrid will take on Gattuso's Valencia in the Spanish Super Cup semi-final on Wednesday.