Jessica Pegula is out of the San Diego Open after Marta Kostyuk overpowered her to reach her first WTA 500 final.
The San Diego Open was the American No. 2's first tournament since the Australian Open. It was also her first event since her surprising split with David Witt, who has now joined the team of Maria Sakkari.
Pegula secured a commanding win in her opening match in San Diego against Jule Niemeier, before following it up with a more hard-fought victory against Anna Blinkova, who defeated Elena Rybakina at the Australian Open.
Kostyuk was always likely to present Pegula's toughest test at the event so far. The Ukrainian reached the quarterfinal at this year's Australian Open, with her powerful game tough for any player to deal with when it is flowing.
Initially, it seemed like Pegula was going to handle the challenge of Kostyuk more easily than expected. However, the match then rapidly got away from the American in a manner that stunned the crowd on Centre Court.
Kostuk's game was a mess at the start of the match. Pegula did not have to do much other than put the ball in the court and wait for her opponent to make a mistake. The six-time Grand Slam quarterfinalist raced into a 5-1 lead.
The set seemed over, but suddenly, Kostyuk hit back. She found her range from the baseline, and the cautious hitting from Pegula was now helping her. The Ukrainian began by retrieving one of the breaks.
Kostyuk then broke again to make it 5-5 by winning an utterly extraordinary rally. Both players covered almost every angle on the court during an exchange of more than 20 shots, before Kostyuk struck a backhand winner down the line.
A tiebreak was eventually needed, and it was Pegula who made more unforced errors throughout it. Another backhand winner down the line saw Kostyuk take the tiebreak 7-4.
The Ukrainian's level was then incredible in the second set. Pegula was fighting as hard as she could, and Kostyuk did have to save three break points in one service game, but that was as good as it got for Pegula in the set.
Kostyuk continued to hit winners all over the court in a way that was close to unplayable. She claimed the set 6-1, and sealed a stunning 7-6 6-1 triumph against Pegula, who will now turn her attention to Indian Wells next week.