ZHUHAI, China, Nov. 2 -- No. 2 seed CoCo Vandeweghe beat Elena Vesnina of Russia 6-3, 6-2 to join Ashleigh Barty and Anastasija Sevastova at the semifinals of the Hengqin Life WTA Elite Trophy Zhuhai on Thursday.

The World No. 12 American won both of her matches in the Bougainvillea Group, assuring herself a place in the final four.

Vesnina struggled with a lower back injury throughout the match and could not cope with power game of Vandeweghe who blitzed her way through the 79-minute encounter with 30 winners, including 11 aces.

Australian upstart Barty also topped the Rose Group with a 2-0 record after overcoming former world number one Angelqiue Kerber 6-3, 6-4.

The 21-year-old Queenslander, who beat Russia's Anastasia Pavlyuchenkova on Wednesday, fired 11 aces to Kerber's 2 to win the match.

Barty earned four break points and converted three of them.

Her powerful serve turned out to be the key of her aggressive game, accoring to Barty.

"I felt like I served great all week and put myself in a good position in my service games to then be super-aggressive," she said.

Kerber, 29, who won last season's Australian Open and US Open, displayed lamentable efficiency as she converted only one break point of all the seven she created.

This is the German's second consecutive loss from as many matches after she lost to Pavlyuchenkova 6-3, 3-6, 6-2 on Tuesday.

Sevastova beat Barbora Strycova of Czech Republic 6-3, 6-4 to seal a place in the semifinals.

Sevastova, 26, finished first at the Camellia Group with two wins.

The Latovian in her career never beat Sloane Stephens and Strycova, her two opponents in the group stage, but did not drop a set in coming out victorious in this WTA season-ending tournament.

She beat Stephens in her opening match, and then triumped in the battle against Strycova.

Sevastova came from 2-0 down in the opening set, winning 20 of the next 24 points and five straight games en route to taking a one-set lead, and later used a decisive late break in the seventh game of the second set to earn victory.

The WTA Elite Trophy is a round-robin tournament for the top players who failed to qualify for the WTA Finals. The tournament splits 12 players in four groups of three, with the group winners reaching the semifinals.

ZHUHAI, China, Nov. 2 -- No. 2 seed CoCo Vandeweghe beat Elena Vesnina of Russia 6-3, 6-2 to join Ashleigh Barty and Anastasija Sevastova at the semifinals of the Hengqin Life WTA Elite Trophy Zhuhai on Thursday.

The World No. 12 American won both of her matches in the Bougainvillea Group, assuring herself a place in the final four.

Vesnina struggled with a lower back injury throughout the match and could not cope with power game of Vandeweghe who blitzed her way through the 79-minute encounter with 30 winners, including 11 aces.

Australian upstart Barty also topped the Rose Group with a 2-0 record after overcoming former world number one Angelqiue Kerber 6-3, 6-4.

The 21-year-old Queenslander, who beat Russia's Anastasia Pavlyuchenkova on Wednesday, fired 11 aces to Kerber's 2 to win the match.

Barty earned four break points and converted three of them.

Her powerful serve turned out to be the key of her aggressive game, accoring to Barty.

"I felt like I served great all week and put myself in a good position in my service games to then be super-aggressive," she said.

Kerber, 29, who won last season's Australian Open and US Open, displayed lamentable efficiency as she converted only one break point of all the seven she created.

This is the German's second consecutive loss from as many matches after she lost to Pavlyuchenkova 6-3, 3-6, 6-2 on Tuesday.

Sevastova beat Barbora Strycova of Czech Republic 6-3, 6-4 to seal a place in the semifinals.

Sevastova, 26, finished first at the Camellia Group with two wins.

The Latovian in her career never beat Sloane Stephens and Strycova, her two opponents in the group stage, but did not drop a set in coming out victorious in this WTA season-ending tournament.

She beat Stephens in her opening match, and then triumped in the battle against Strycova.

Sevastova came from 2-0 down in the opening set, winning 20 of the next 24 points and five straight games en route to taking a one-set lead, and later used a decisive late break in the seventh game of the second set to earn victory.

The WTA Elite Trophy is a round-robin tournament for the top players who failed to qualify for the WTA Finals. The tournament splits 12 players in four groups of three, with the group winners reaching the semifinals.