The Brazilian defender was known as both a skilled, ball-playing centre-back and an accident waiting to happen during his first spell at Stamford Bridge, but has been a rock in Conte’s three-man central defence.
Luiz was a cult figure for the Blues due to his attacking ability and propensity for banging in free-kicks from long range, but has also been solid and reliable since his return from Paris Saint-Germain.
"David arrived in England and I heard a lot of bad things about him when he arrived, and why was he coming back in Chelsea because, in the past, he had performed bad and he was 'not a defender', This was a great challenge for him, but also for me," Conte said.
"For me. Because I think when you have great ability for your players, and you can work to try and improve some situations, it's great. You can see that David, for sure, is a really strong defender.
"I like, always, to repeat to him that it's very important to have the right concentration. His role is a crucial role for us, and I think he has performed very well. But I want him to perform very well for the rest of the season.
"I read in the newspapers, a lot of bad considerations, saying we had spent a lot of money on him and, in the past, he hadn't been very good as a defender. For this reason, he had played as a midfielder.
"I heard a lot of these things. But when we decided to buy him, to take him back, we were sure. We were sure we were taking a really good player and put him again as one of the best defenders in Europe and, I hope, in the world."
Other managers have tried to push Luiz from central defence into a holding midfield role, but Conte believes the Brazilian is best in his favoured back three.
"I think this position is perfect for David to play as a central player in three defenders," Conte added. "This is the best position for him because he has good technique, he's strong, he can start our possession and the personality to do this.
"He also has two really good defenders at his side, in Gary [Cahill] and [César Azpilicueta] or [Kurt] Zouma or [Nathan] Ake or John [Terry]. This position is fantastic for him. He's performing very well."