Sixth-seed Marta Kosytuk of Ukraine and British No. 1 Katie Boulter will play for the 2024 San Diego Open title after a day of semifinal upsets at a rainy Barnes Tennis Center.
Kostyuk stunned top seed Jessica Pegula, 7-6(4), 6-1, while Boulter upended third-seed Emma Navarro, 6-3, 6-1, to end hopes of an all-American final.
Both players will be part of their first final at the WTA 500 level when they face off after 4 p.m. Sunday.
The No. 5-ranked Pegula looked to be in control early on, racing out to a 5-1 advantage in the opening set. However, her opponent reeled off five unanswered games to force a tiebreak and snatch the momentum for good.
It marked the first win for Kostyuk, 21 over Pegula in three tries. Ranked 34th, she finished with 26 winners to 23 unforced errors, including nine double faults.
“I lost to Jess in our previous match very easily [in the third round of the 2023 Australian Open]. I was very disappointed it was going in that same direction,” she said. “I don’t even know how I turned this around.”
Pegula, 30, was playing her first tournament since the Australian Open, having withdrawn from Doha and Dubai with a neck injury.
A British player hasn’t reached the semifinal of a WTA 500 event since Johanna Konta did so in 2018 in Moscow). But Boulter looked comfortable in Barnes Stadium, where she overpowered Navarro.
She would win 87% of her first-serve points and save both break-points she faced in the rain-interrupted, one-hour, 14-minute contest.
Boulter, 27, has now taken down two of the top three seeds in San Diego, having come from a set down to beat second seed Beatriz Haddad Maia of Brazil in Round 2.
“Honestly, at the start of the week, I didn’t think I’d be in this position,” said Boulter, now 6-1 against seeded opponents on the year. “I’ve been working so hard with my team. Just to be here in this position, I’m very grateful.”
The 2023 Nottingham champion is headed for only the second tour-level final of her career. It will be her first encounter with Kostyuk.
The doubles final, at 1:30 p.m. Sunday, matches No. 1 seeds Desirae Krawczyk and Pegula against No. 3 Nicole Melichar-Martinez and Ellen Perez.