The French champions have struggled to find their form in the early part of the Ligue 1 season, drawing five of their eight matches so far.
An injury to captain Thiago Silva has seen Luiz thrown into first-team action sooner than Blanc would have liked, and the coach says it is only natural that the defender - signed from Chelsea during the close-season - might struggle early on.
"He needs time," he said. "Like some other players, he arrived after a big disappointment in the World Cup.
"He had almost no pre-season preparation when he came here. He plays games with no preparation through friendy games. He came and played directly.
"Maybe it was better to wait before including him in the line-up. But with Thiago Silva's injury, we couldn't.
"But I think he is doing very well, because he brings his impact.
"He is reassuring even if he takes some risks sometimes. But he is reassuring.
"I think he's a great defender, and he is becoming more and more important to this team."
PSG host Barcelona in the UEFA Champions League on Tuesday.
