Pep Guardiola improved Douglas Luiz by "70 per cent" despite the Brazilian working with the coach for just a few months across his time at Manchester City.
Douglas Luiz joined City from Vasco da Gama as a teenager in 2017 but was swiftly sent out on loan to Girona for the 2017-18 season, before returning to the Spanish side for the following campaign.
Those temporary moves came either side of a full pre-season Douglas Luiz spent with Guardiola and the City senior squad, while he also teamed up with them briefly ahead of his permanent move to Aston Villa last July.
Although Douglas Luiz's exposure to Guardiola's coaching methods was limited, he was still able to appreciate just how good the former Barcelona and Bayern Munich tactician is.
"I have no words to explain him," Douglas Luiz told Vasco TV. "He's a guy who is focused on football, his life is football.
"For me, he is the best coach in the world. In two months, the guy managed to evolve more than 70 per cent of my potential.
"I have a lot of affection for him, I thank him so much for everything he did. I feel very honoured to have this affection from a great coach, who for me is the best, for my football."
Despite a promising second season with Girona and training with City's first team, when an offer reportedly worth £15million arrived from Villa, Douglas Luiz's days at Etihad Stadium were over.
It came as a surprise to the midfielder and, while City inserted a buy-back clause in the deal, at Villa he feels he has found a home not too dissimilar to Vasco.
"I didn't expect to be sold, but I think God knows everything," he said. "I am very happy in this great club that, for me, is like Vasco.
"It has its 'cauldron' [stadium], it has a very passionate crowd for the club. It is a club that is recognised throughout the country, and I'm sure the club is very happy.
"There is a clause that Manchester City can buy me in those first two years."