Belinda Bencic bounced back from her US Open exit in emphatic fashion by defeating qualifier Xu Yi-fan 6-0 6-0 in the Toray Pan Pacific Open first round.

The Swiss needed just 43 minutes to wrap up the victory in her first match since losing to Venus Williams in the third round at Flushing Meadows.

Bencic hit 21 winners and made just four unforced errors, setting up a second-round meeting with 2011 US Open champion Samantha Stosur, who came from a set down to beat Alison Riske 4-6 6-1 6-3.

Fifth seed Angelique Kerber was similarly impressive but against a tougher opponent, the fifth seed seeing off world number 39 Daria Gavrilova 6-2 6-2 in Tokyo.

Kerber needed only 25 minutes to prevail in the first set and eventually closed the match out in a second set that featured six breaks of serve.

"I knew Daria from good matches in the past, so I actually knew it would not be an easy one," Kerber said. "At the end I was playing well and that's the key for me - playing my tennis."

Carla Suarez Navarro, seeded sixth, also progressed, overcoming Kateryna Bondarenko 7-6 (7-3) 6-2, while Dominika Cibulkova was the beneficiary of a retirement against Mirjana Lucic-Baroni, who withdrew when trailing 6-4 1-0.

Madison Brengle made short work of Zarina Diyas, winning 6-2 6-2, and Elina Svitolina required less than an hour to see off Olga Savchuk 6-2 6-0.

Elsewhere, qualifier Ana Konjuh beat Kristina Mladenovic 6-0 3-6 6-3 and Kurumi Nara won the all-Japanese clash with Misaki Doi 7-6 (7-1) 6-2.