Americans Danielle Collins and Katie Volynets earned quarterfinal victories on home soil at the inaugural ATX Open in Austin on Friday.

No.4 seed Collins overcame Anna Kalinskaya 3-6, 6-2, 6-1 to reach her first WTA semifinal of the season. Collins, a former Top 10 player and the 2022 Australian Open finalist, took 1 hour and 47 minutes to earn her second win over Kalinskaya in their two meetings, both this year.

"[Kalinskaya and I had] a tough match in Australia," Collins said after her win. "I really expected to play a long match, a hard match against her, because she’s been performing very well and really taking off with her game."

Collins will face No.8 seed Marta Kostyuk for the first time in Saturday's semifinals. Ukraine's Kostyuk moved into her first semifinal of the year by defeating Anna-Lena Friedsam of Germany 7-6(6), 6-2.

"[Kostyuk is a] very aggressive player, she’s been having a really great year so far," Collins said. "I’ll have to be ready to get back some really strong shots and just go out and try to play my best tennis, because that’s what it will take to beat her."

Earlier, Volynets grabbed a 7-5, 6-3 win over Peyton Stearns, in a battle between 21-year-old Americans who were both contesting the first WTA quarterfinals of their careers.

“I’ve known [Stearns] probably since I was 12 years old, which makes the match never easy to play, for either of us," Volynets said afterwards. "I’m sure both of us were feeling some nerves. Despite that, I think we were able to have a great match.”

Highlights: Volynets def. Stearns

Volynets took 1 hour and 44 minutes to notch her first tour-level semifinal appearance, holding off comebacks by Stearns in both sets, from 5-2 and 5-0 down respectively.

"I was able to do a good job to get leads in both sets, and then I didn’t execute how I wanted to," Volynets said. "I think it was important that I gave myself a lot of opportunities, so that helped me to close.”

Stearns still had a positive week, earning her first tour-level match-wins in her return to Austin, home of the University of Texas. Stearns was one of the stars of UT's tennis team, winning the NCAA singles title last year as a sophomore before turning pro.

Highlights: Gracheva def. Stephens

In the semifinals, Volynets will face Varvara Gracheva, who upset No.5 seed Sloane Stephens 7-6(4), 6-3 in the late quarterfinal. Gracheva moves into the second WTA semifinal of her career, and her first since Chicago in 2021.

Gracheva avenged her loss to Stephens last week in the Merida second round, where the American prevailed in a third-set tiebreak. Gracheva now holds a 2-1 lead in her head-to-head against 2017 US Open champion Stephens.