Australia's top two brushed aside their first-round opponents at the Wuhan Open on Monday, with straight-sets victories in the $2.7-million tournament for both Ashleigh Barty and Daria Gavrilova.

Barty, the Australian No 1, downed Britain's Johanna Konta 7-5, 6-4 to progress, and could face Wimbledon champ Angelique Kerber in the third round.

But it was Gavrilova, the Aussie No 2, who caused the biggest upset of the Wuhan Open so far, dumping out 10th-seed and last year's French Open winner Jelena Ostapenko 6-2, 6-4.

The Latvian, who reached the Wuhan semifinals last year, mounted a spirited fightback in the second set but was unable to contain her unforced errors and appeared frustrated as Gavrilova held steady to secure the win.

Ostapenko "is a quality player, she always fights and comes (out) firing... so I expected that," Gavrilova said after the match.

It has been a September to forget for Ostapenko, ranked 12th in the world.

Last week, her defence of the Korea Open title was ended in the second round by then-122nd-ranked Ekaterina Alexandrova.

Gavrilova could now face another tough challenger in the third round: Karolina Pliskova, who downed US Open champ Naomi Osaka in straight sets in Tokyo on Sunday to win the Pan Pacific title.

Nine of the world's top 10 are in action at the Wuhan Open as the 2018 WTA season enters its final stretch and the frenzy for ranking points intensifies. Japanese star Osaka, the current No 8, had to withdraw due to illness.

In addition to $500 000 in prize money, the winner will also lock down 900 points.

In other matches on Monday, the 18th-ranked Madison Keys of the United States defeated China's Wang Yafan, and 14th-seed Garbine Muguruza eased past Belgium's Alison Van Uytvanck 6-4, 6-0.

An ankle injury forced American Coco Vandeweghe to retire in the third set against Donna Vekic.

World No 1 Simona Halep will begin her Wuhan challenge against Dominika Cibulkova on Tuesday.