Chelsea's Antonio Conte claims David Luiz is not too old to develop into one of the world's best defenders.
The Brazilian moved to Stamford Bridge for a second time last week, returning from Paris Saint-Germain after two years in France.
And, although Conte acknowledges David Luiz needs to work on areas of his game, he believes the 29-year-old still has time to improve.
"I think that every player, up until the end of their career, can improve," he told a news conference ahead of Chelsea's game against Swansea.
"I know when you are 32, 33, 36, you always can improve. I think this from my experience as a footballer.
"David Luiz is 29, it's a fantastic age for him to become one of the best defenders in the world.
"I see great commitment from him. He wanted to play for Chelsea. This is a great opportunity for him and for us to improve.
"He has good characteristics to become one of the fantastic defenders in the world."
Conte added David Luiz's arrival may allow him to use a 3-4-3 formation, and also suggested the Brazil international will have a positive impact in the dressing room.
"We took a player with a great personality and good technique," he said. "I like to play football and I like the defenders to play football.
"David can improve in defensive situations, but I am very happy to have him here. He's a good guy and a positive guy in the dressing room."