It was a stunning backhand passing winner down the line that cracked open the first set for Paula Badosa on Friday, propelling her to a 7-6(4), 6-2 victory over Coco Gauff in a marquee quarterfinal at the Mubadala Silicon Valley Classic.

No.2 seed Badosa and No.6 seed Gauff were deadlocked at 3-3 in the first-set tiebreak when Badosa swiped a key point with the shot, giving the Spaniard the first mini-break after coming back from a break down in the set.

Badosa won three of the next four points to take the one-set lead — helped along by double faults by Gauff on the final two points — and then eased through the second set to move into her fourth semifinal of the season.

"It’s never easy to start against such an aggressive player with a big serve," Badosa said afterward. "I think I adapted pretty well in the [end] of the first set, and I played a pretty perfect tiebreak, so I’m really happy about that."

World No.4 Badosa improved to 2-1 against Gauff as her wild adventure through San Jose continues. Badosa barely scraped past American qualifier Elizabeth Mandlik on Thursday, coming back from a break down in the final set before prevailing over the World No.240 in a third-set tiebreak.

On Friday, Badosa had to fight back from a break down in the first set, but once she slammed her fiery backhand pass to help take control of the breaker, she eased through the remainder of the match relatively comfortably.

Badosa played a clean, powerful match, with 17 winners to 15 unforced errors, and she converted four of her eight break points. Gauff's 21 winners were undone by 29 unforced errors, including a total of six double faults.

Badosa will now face No.7 seed Daria Kasatkina in the San Jose semifinals on Saturday. Kasatkina outlasted No.4 seed Aryna Sabalenka 4-6, 7-5, 6-0 earlier on Friday.

Highlights: Kasatkina def. Sabalenka

World No.12 Kasatkina maneuvered to a 2-hour and 23-minute comeback victory over Sabalenka as she defeated a Top 10 player for the fourth time in 2022. Kasatkina has reached the quarterfinals or better five times in her last six events.

Badosa and Kasatkina have faced off twice before, both times this year. Badosa cruised to a 6-2, 6-2 win in the Sydney semifinals on hard court in January, but Kasatkina leveled their head-to-head with a 6-4, 6-4 victory in the Round of 16 on the clay of Rome.

"She’s winning a lot of matches, she’s winning against the best players in the world, she’s doing an amazing year," Badosa said about Kasatkina.