Seventh-seeded Angelique Kerber of Germany beat local favourite Naomi Osaka 6-3 6-4 on Monday to advance to the second round of the Pan-Pacific Open.
The victory was additionally sweet for Kerber, who was looking for revenge after the Japanese teenager knocked her out of the US Open in straight sets.
"It's always tough to play against her," Kerber said. "I was trying to come out here and really focus on every single point and make it better than last time. ... She's a great player and a tough opponent. For sure she will have great success in the future."
Osaka lost to Caroline Wozniacki in the final of last year's tournament.
Kerber will play either Madison Brengle or Daria Kasatkina in the next round.
Meanwhile China's Wang Qiang inflicted a 'double bagel' on eighth seed Kristina Mladenovic of France in the first round of the Pan Pacific Open on Monday.
Wang needed 48 minutes to seal the 6-0 6-0 win over the world No.15, who also suffered first round defeats at the US Open and in Connecticut, Cincinnati and the Canadian Open.
Also, wildcard Kurumi Nara of Japan overcame a slow start to oust Yulia Putintseva of Kazakhstan 2-6 6-4 6-2, while China's Wang Qiang beat Kristina Mladenovic of France 6-0 6-0.
Meanwhile, organisers announced that Agnieszka Radwanska, a two-time tournament champion, had pulled out of the tournament due to a virus. The 11th-ranked Pole was seeded sixth.
