Luiz is certain Chelsea have a player who is destined to be one of the world's best when he overcomes his shyness.
"I try to help him every day with this," said Luiz. "I tell him he's an amazing player with the talent to make the difference and change every game. I tell him to be happy and trust in his football. Some players need this. My job is to give confidence to the guys like Oscar.
"He is so shy but I say, 'Come on, you have the quality to be in a side with the best players in the world and you have the opportunity to show that'.
"Some guys in Brazil don't, they have the quality but they don't have the opportunity to come to Europe and show the world what an amazing player they are. So, I say, 'Come on, don't be shy, show your quality'."