Barty, Sevastova storm into Zhuhai semis

Ashleigh Barty and Anastasija Sevastova booked their semifinal spots without dropping a set in the round-robin phase of the WTA Elite Trophy in Zhuhai, south China's Guangdong Province, on Thursday.

Barty, the Australian who is the youngest player in the draw, posted a 6-3, 6-4 win over former world No. 1 Angelique Kerber to top the Rose Group with a 2-0 record.

The 21-year-old struck a staggering 35 winners to just 12 unforced errors in a dominant performance. Barty, seeded ninth, posted her first victory over Kerber after losing their only previous meeting in Brisbane at the start of the season.

"It was tough group for me because I hadn't actually beaten either of those girls," Barty, who beat Russian Anastasia Pavlyuchenkova in her first group match, told reporters.

"It's nice to sort of get that revenge this week, but I felt like I served great all week and put myself in a good position in my service games to then be super-aggressive and nice and clear when returning."

Sevastova, making her tournament debut, posted a perfect record in Camellia Group with a 6-3, 6-4 win over Barbora Strycova of the Czech Republic.

The Latvian came back from 0-2 down in the opening set, winning 20 of the next 24 points to take the first set, and later claimed a break in the seventh game of the second set to earn the victory.

"I feel it's my best Asian tournament this year, so I feel great in Zhuhai," Sevastova said.

"I haven't been playing so well in China, in Asia, particularly, but here somehow it suits my game, I think, the court, the balls."

Later in the day, American CoCo Vandeweghe also progressed to the final four with a 6-3, 6-2 win over Russian Elena Vesnina, who was struggling with a back injury throughout the match.

The tournament in Zhuhai features the leading players on the women's tour who didn't qualify for the WTA Finals in Singapore last week. The 12-player draw is divided into four groups of three, with the winner of each group advancing to the semifinals.

In Paris, Juan Martin del Potro is relishing the "battle" to qualify for the World Tour Finals after beating Robin Haase 7-5, 6-4 in the Paris Masters last 16 on Thursday.

The former US Open champion can take the eighth and final qualification spot for London from Pablo Carreno Busta if he reaches the semifinals at Bercy, and he will face either John Isner or sixth seed Grigor Dimitrov in the last eight.

"It's going to be a good battle next round trying to qualify for London," said Del Potro.

"But anyways, I think I have two ways to take, one is London, one is my home and vacation.

"Both ways are great to me, but of course, I would love to reach London once again."

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The 13th-seeded Argentinian had little trouble in seeing off Dutchman Haase, who had notched his first win over a top-five player against Germany's Alexander Zverev on Wednesday.

Three successive breaks of serve left Del Potro serving for the first set, which he took on his fourth set point.

The 29-year-old grabbed the crucial break in game five of the second set, before closing out a comfortable victory.

Del Potro, who was 47th in the 'Race to London' standings before the US Open, is now one win away from reaching his fifth semifinal in six events.

His incredible run of form included a victory over Roger Federer en route to the last four at Flushing Meadows and a second straight Stockholm Open title.

If Del Potro reaches the Paris semis, Frenchman Lucas Pouille would have to win the tournament to deny him a spot at the year-ending eight-man event for the first time since 2013.

Del Potro has suffered from a long list of injuries since he broke through with US Open glory eight years ago and was ranked 590th at the end of 2015, but he now stands on the brink of a return to the world's top 10.

"It could be a fantastic moment for me," he added.

"I didn't expect to get this close to qualifying for London.

"And everything is very amazing after all my problems, all my injuries... I love to surprise myself, and that's what I'm doing now."

Veteran Spaniard Fernando Verdasco knocked out Austrian fifth seed Dominic Thiem with a 6-4, 6-4 victory to reach his first Masters quarterfinal since 2012.

The 33-year-old left-hander had never previously been past the third round in Paris, but he progressed to a last-eight clash with either American Jack Sock or Pouille, who play later on Thursday.

Spanish great Rafael Nadal takes on Uruguayan Pablo Cuevas, having already secured the year-end world No. 1 ranking.