BEIJING — Bianca Andreescu had two reasons to smile on Monday.

The Canadian tennis star won her first match since triumphing at the U.S. Open on Sept. 7 and also found out she has secured a spot in the WTA Tour Finals later this month.

Andreescu, 19, overcame a rocky second set to beat Aliaksandra Sasnovich of Belarus 6-2, 2-6, 6-1 in the first round of the China Open. Her 14th win in a row came hours after the WTA said she had locked down one of eight berths in the season-ending Finals, Oct. 27 to Nov. 3 in Shenzhen, China.

"I'm on a roll right now. Hopefully I can just keep it up because I think it gives me a lot of confidence," Andreescu said.

The 60th-ranked Sasnovich had her chances against the world No. 6, but notched just four of 16 break points.

Andreescu, from Mississauga, Ont., won 70 per cent of her points on first serve, as compared to 56 per cent for Sasnovich.

It was Andreescu's 13th win in a row in a three-set match.

Next for Andreescu is a rematch of a U.S. Open quarterfinal against Elise Mertens of Belgium.

Elsewhere, former top-ranked players Venus Williams and Simona Halep both lost in the second round.

Williams lost 3-6, 6-3, 7-5 to ninth-seeded Belinda Bencic of Switzerland, who saved two match points in the final set to outlast the seven-time Grand Slam champion despite making 40 unforced errors in the match. She will next face the winner of seventh-seeded Petra Kvitova and Kristina Mladenovic in the round of 16.

Halep, the reigning Wimbledon champion, lost 6-2, 6-3 to unseeded Russian Ekaterina Alexandrovam, who earned just her second career win against a top-10 opponent. Halep was playing on back-to-back days after defeating Sweden's Rebecca Peterson on Sunday. The Romanian has been nursing a back injury that forced her to retire at Wuhan last week.

"It was a tough one today. I didn't recover well after my first match, so it was very tough for me to play and she played really well," Halep said. "The injury from Wuhan, it's getting worse, so I have to go home and take an MRI ... take a break and do some treatment."

Defending champion Caroline Wozniacki hit seven aces as she cruised past American qualifier Lauren Davis 6-1, 6-3 in her opening match of the tournament. The former No. 1 will face another American, Christina McHale, in the second round.

In her first match since winning the U.S. Open, Canada's Bianca Andreescu ousted Aliaksandra Sasnovitch of Belarus 6-2, 2-6, 6-1.

Meanwhile, Ottawa's Gabriela Dabrowski and her partner Yifan Xu of China secured a spot in the doubles portion of the WTA Finals on Monday.

Dabrowski and Xu also advanced to the quarterfinals at the China Open with a 6-4, 7-5 win over Danija Jurak of Croatia and Maria Jose Martinez Sanchez of Spain.

In the men's tournament, second-seeded Alexander Zverev beat Frances Tiafoe 6-3, 6-2, while fourth-seeded Karen Khachanov of Russia defeated Pablo Cuevas 6-2, 7-6 (7).

Montreal's Felix Auger-Alessiame opens against Spain's Albert Ramos-Vinolas on Tuesday.

— with files from The Associated Press

This report by The Canadian Press was first published Sept. 30, 2019.