Zheng Saisai kept sending back those big, looping groundstrokes and digging balls from every corner to keep points alive as Aryna Sabalenka became more and more frustrated not to be thriving in her typical power game.

Zheng of China stayed steady and patient to capture her first career singles title, beating Belarusian Sabalenka 6-3, 7-6 (3) in the Mubadala Silicon Valley Classic on Sunday.

"It brings out so much confidence," Zheng said. "I wasn't winning and this week I beat many seeds. This gives me confidence but still I'm just going to play my tennis."

Zheng, who is ranked 55th and played one more match than Sabalenka to reach Sunday's championship, topped three seeded players on the way to her second career final and then another for her first victory at age 25. She was runner-up at Nanchang last year.

With her big topspin shots landing deep and the defensive ability to chase down balls all over the court, Zheng flustered opponents all week with her consistency and level-headed play — and the emotional Sabalenka was no different.

Not that Zheng was paying attention to her opponent's outbursts, saying she stayed focused on her own game plan.

"The tactic is put the ball deep and whenever I see a space let her run and change if I can flies or high balls because if I give her the same pace, the same ball, she will hit winners on any corner, so I was just trying to mix it up," Zheng said.

Sabalenka threw her racket after double-faulting on the first match point, slammed her racket to the court following another mistake and also hit it on the net in frustration in an afternoon of unforced errors after the 21-year-old missed on a fourth career title. The second-seeded Sabalenka, who lost in the first round of qualifying here in 2018, rode her powerful first serve to reach to her seventh final and is projected to match her career-high ranking of ninth.

Her power was neutralized by Zheng's regular topspin on both sides, timely lobs and array of shot-making to keep Sabalenka guessing.

"I couldn't do anything today with myself. I couldn't control my emotions. I was screaming some (stuff), I was throwing the rackets," she said. "... Her game destroyed me because I couldn't use my power. I wasn't ready for that."

Zheng's victory could propel her to No. 38 — matching her career best — when Monday's new singles rankings are released.

The two met once previously, with Zheng winning in straight sets on the ITF circuit in 2017. Each woman had played one three-set match this week.

They even wore matching Nike outfits for the final of dark skirts and a gold tank.

For Sabalenka, the loss will provide lessons in how to be more mentally tough. She noted, "I want to be like Serena on the court."

"I expect better tennis than I played today," she said. "I just need to be calm on the court and just play my tennis and don't care about anything else."

Venus Williams lost her opening match Tuesday night after reaching last year's quarterfinals here. The 39-year-old, seven-time Grand Slam champion was in the field for the 15th time, this year as a wild-card entry.

In the doubles final, Kveta Peschke of the Czech Republic and American Nicole Melichar defeated Japanese tandem Shuko Aoyama and Ena Shibahara 6-4, 6-4 earlier Sunday.

This marked the second year the event has been played at San Jose State University after moving from Stanford.