Chelsea boss Carlo Ancelotti admits David Luiz still has much to learn.
Ancelotti concedes Luiz was lucky to stay on the pitch for their victory over Manchester United.
Ancelotti said: "He has to know English football. He has to be more calm on the pitch.
"Obviously he's showed fantastic ability and quality.
"He has to improve, but he will because he'll have more experience and knowledge about English football. He can change his behaviour on the pitch."
Luiz's performances have made him an instant hero among Chelsea fans and Ancelotti believes there is even more to come from the outrageously-gifted Brazilian.
"He's showing fantastic ability offensively, obviously," he said.
"He's able to pass the ball and move in front without problems. He's able to shoot at goal.
"Defensively, he can improve. He can be better defensively."
