World No. 1 Naomi Osaka started her BNP Paribas Open title defense on a winning note Saturday after beating Kristina Mladenovic to reach the third round of the tournament.

The top seed from Japan posted a 6-3, 6-4 victory over France's Mladenovic at the Indian Wells Tennis Garden, where she won her maiden title a year ago. Osaka, playing her first match under new coach Jermaine Jenkins, fired five aces against Mladenovic's one and sealed the win in 1 hour, 21 minutes.

"I've never been a defending champion before, so that was really new and I was super nervous. So I'm glad I could just win," she said in an on-court interview.

Osaka exacted revenge over the 65th-ranked Mladenovic, who had beaten her in the first round at February's Dubai Tennis Championships. That match was Osaka's first after the Australian Open, where she won her second straight Grand Slam event and rose to No. 1 in the world.

"The last time I played her I lost so anything is a bonus after that," said Osaka, who won the U.S. Open. "But she's a really great player and I knew it wouldn't be easy so I just came up here and tried to pump myself up and I did that well."

The hard-hitting Osaka played aggressively from the start and kept her opponent under pressure. She broke Mladenovic's serve at 2-2 before taking a 4-2 lead in the first set.

Osaka kept her rhythm in the second set despite double faulting when she was serving for the match. She will face No. 25 seed Danielle Collins in the third round.

Osaka announced on social media last month that Jenkins, who was recently hired as the United States Tennis Association national women's coach, has joined her team. She had abruptly parted ways with her former coach Sascha Bajin after January's Australian Open.

Among other Japanese players, Misaki Doi lost to former world No. 1 Karolina Pliskova 6-7(4), 6-1, 6-1.

Yoshihito Nishioka beat No. 21 seed Roberto Bautista Agut of Spain 7-6(3), 6-4 in the men's draw. Sixth-seeded Kei Nishikori, who will compete at this tournament for the first time in two years, is scheduled to play Adrian Mannarino on Sunday.