SAN DIEGO -- Unseeded Katie Boulter of England capped a run of upsets to win the San Diego Open singles title with a 5-7, 6-2, 6-2 victory over sixth-seeded Marta Kostyuk of Ukraine on Sunday.
A 10-year tour veteran, the 27-year-old Boulter won her second pro singles title with her fifth straight victory over higher-seeded players in the week-long WTA 500 event.
"I can't stop smiling," Boulter said. "I've been wanting this my whole career and now I've got to move my goalposts and keep it going."
As darkness fell early in the match -- twice delayed by intermittent showers -- both players appeared to struggle while adjusting to the unseasonably cool, windy and drizzly conditions with temperatures in the mid-50s.
In her San Diego Open debut, Boulter shook off a flurry of early first-set unforced errors, initially flustered by Kostyuk's quickness and athleticism. But showing signs of resilience that would later serve her well, Boulter overcame five set points before she sent an errant forehand past the baseline to fall 7-5.
Undeterred, Boulter found her rhythm en route to winning the second set, which was marked by furious backcourt rallies.
About 30 minutes later, Boulter was serving for the match at 5-2 when she struck a crosscourt forehand just out of Kostyuk's reach to give her the title.
"I don't even know where to begin, I'm so happy," said Boulter, who is 6-1 against seeded opponents this year. "When I came here, I really didn't think I would be holding this trophy. Everyone here has been so warm and welcoming to me."
Referring to her 21-year-old opponent, Boulter added: "You're so young and so talented, Marta. I know your time will come."
Kostyuk paid tribute to her family in Ukraine after the match.
"I don't want to make this too sad, but first of all, I want to say hello to my family back in Ukraine," she said. "It's been a difficult time for them and I don't know what's going to happen tomorrow, but there's no one who wants me to win more than they do."
Boulder, who said the cool conditions made her feel at home, was awarded a ceremonial surfboard -- a nod to the event's close proximity to the Pacific Ocean.
"Sorry I didn't get the surfboard this year," Kostyuk said. "But maybe I'll get one next year."
Held at the Barnes Tennis Center, the San Diego Open is a WTA Tour 500 event with a total purse of $922,573, presented by Cymbiotika.