Jessica Pegula loses 12 of last 14 games to Marta Kostyuk in San Diego semifinal stunner

You need a little bit of everything to go your way in order to win a set after trailing it 1-5. Perseverance, your opponent letting you off the mat a bit, some good fortune: these are just some ingredients in the comeback recipe.

So it was fitting that as Marta Kostyuk completed such a comeback in the first set Saturday night against Jessica Pegula, she got all of those things in a single point:

The drastic shift in fortune said plenty about Kostyuk, a talented ball striker who might be even more dangerous with nothing to lose, but perhaps more about Pegula. The world No. 5 and top seed at the Cymbiotika San Diego Open, Pegula is looking for a change with an unexpected coaching switch. It's also been made known that the 30-year-old has talked with Andy Roddick, specifically about her serve.

For all of Pegula's strengths, closing out players in sets and matches has never been automatic. Her serve is the weakest part of her game, and when you combine that with the low-margin strokes she employs—streaky, if often to great effect—it can lead to prolonged slumps lets her opponents stay alive.

Again, all credit to Kostyuk, but this collapse feels like it was more on Pegula's racquet, and maybe even her mind. Her tennis may be more of a work in progress than usual this month, which could be jarring to longtime observers and supporters.

"Just would not expect that," Tennis Channel's Tracy Austin said of Pegula's poor run of play.

It continued in the second set, with Pegula unable to generate any easy service games. Kostyuk broke early and took a 2-0 lead, then broke again at 3-1 and consolidated for her own 5-1 advantage.

"She's being picked apart today, Pegula," said the world feed commentator.

"Not many can do that," added Austin.

Kostyuk saw what can happen when a player doesn't put their adversary away with a big lead—so she immediately broke Pegula and for the match. In all, the Ukranian won 12 of the last 14 games and broke Pegula five times. She'll move on to face Katie Boulter—who defeated third seed Emma Navarro, and has also topped Pegula in 2024—in an unlikely but compelling final.