WASHINGTON: US top seed Jessica Pegula saved four match points to eliminate two-time Australian Open champion Victoria Azarenka on Friday (Saturday in Manila) and advance to the WTA Charleston Open semifinals.

Pegula squandered four match points at the clay court event before denying Azarenka's four chances to advance and finally captured a 6-4, 3-6, 7-6 (9/7) victory after two hours and 36 minutes when Azarenka hit a forehand service return long.

"That was an emotional roller coaster," Pegula said. "It was like that the entire match. I was playing really well, and then I got frustrated I didn't break in the second, and she kind of turned it up a gear.

"I was able to get back in the third, but it was really up and down; I feel like, from the end of the second, start of the third.

"At the end, it was really windy, so a lot of awkward points. It's tough when it's windy, playing with your nerves as well. I'm just happy I got through."

Pegula advanced to a Saturday semi-final against fourth seed Daria Kasatkina, who battled back to beat Romania's Jaqueline Cristian 6-7 (4/7), 6-2, 6-3 after two hours and 42 minutes.

Miami Open champion Danielle Collins, who won twice on Thursday to reach the quarter-finals, ousted Belgian 11th seed Elise Mertens 6-3, 6-4, stretching the American's win streak to 11 matches.

Collins, who ousted 2023 champion Ons Jabeur and fellow American Sloane Stephens on Thursday, will face Greek third seed Maria Sakkari in the semi-finals after she eliminated ninth seed Veronika Kudermetova 6-2, 6-4.

Pegula equalized her rivalry with Azarenka at 3-3, but only after a tenacious third-set finish.

"We were playing some good tennis there at the end," Pegula said. "I had match points, 40-love on her serve, and that's frustrating, but I was just trying to stay focused to win, and at the end, I don't know what happened — I have no idea.

After squandering her chances for the victory, then falling behind 6-3 in the tie-breaker, Pegula admitted she was less than confident.