Antonio Conte says he is not surprised at David Luiz's new-found defensive competence and hinted the Brazil international would continue to keep John Terry out of the side for Saturday's visit of Everton.
Chelsea re-signed Luiz from Paris Saint-Germain in August, two years after selling him to the Ligue 1 champions after coming to the conclusion he did not possess the attributes of a top defender.
Since his return, however, he has helped form a formidable three-man backline alongside Gary Cahill and Cesar Azpilicueta to help Chelsea rebound from a bad start to the season to move up to fourth in the Premier League table.
Asked if Luiz's form had come as a shock, Conte told a news conference: "I'm not surprised because I knew David Luiz as a good defender, a good player with a great personality and a good technique.
"We are working with him and the other defenders to create a solid defence.
"He's a good player and has won a lot in his career but he must continue to win. For this reason he is at Chelsea, we wanted to buy him for this reason.
"But every single player can improve. This way of playing is good for him, but I know we can improve, not only a single player but the whole team."
Luiz's excellence has meant captain Terry has had to be content with a place on the bench.
Conte added: "It is difficult to change the team when we're playing well.
"John is available, he is in good form after his ankle injury. He's trained with us for a second week and is in good form. I don't see any problem."