Ntilikina scored 17 points and added a rebound, two assists and a steal to go with three turnovers in a 128-100 loss to the Golden State Warriors.
Ntilikina replaced Trey Burke, who had started the Knicks' first five games.
Fizdale said he was pleased with how the Knicks' starters played against Golden State, but he felt his team grew complacent in the fourth quarter.
"I just saw that look of, 'All right, we've done enough tonight. We played hard enough,'" Fizdale said. "I just got to get these guys to understand how to play 48 minutes. Right now we're playing college ball. Forty. We have 3½ really good quarters, and with a champion, that's not enough."
"Coach said he wants me to lead the second unit. So I'm just leading the second unit," Kanter said.
Fizdale has said that he may change the lineup regularly early in the season to evaluate different player combinations. The first-year Knicks coach said that one of his goals in changing Friday's lineup was to see Ntilikina at point guard. Ntilikina, whom the Knicks drafted with the eighth overall pick in 2017, played lead guard overseas before coming to the NBA.
Fizdale said Ntilikina played well against Golden State.
"He made us go. He picked his spots. He didn't pass up much," Fizdale said. "I really thought he got after it defensively. He competed hard. The guy he is competing against (Stephen Curry) is one of those special talents, once-in-a-lifetime talent."
The Knicks have lost five straight after their season-opening win over the Atlanta Hawks.