(Photo credit: David Kirouac-Imagn Images)

Anastasija Sevastova saved nine of 13 break points on Friday while recording a 3-6, 6-4, 6-1 victory over two-time defending champion Jessica Pegula in the third round of the National Bank Open in Montreal on Friday.

Sevastova of Latvia had a first-serve percentage of 71 percent while rallying to upend the third-seeded Pegula.

Sevastova, 35, had a hard time explaining what happened.

'Somehow, I was down 2-0 in the second set and started to play better and better,' Sevastova said. 'Third set, I played really good. Just trying to stay on the court as long as possible.'

Pegula appeared to be sailing when she won eight of the first 11 games. But Sevastova won the next four games to jumpstart her comeback.

After winning the second set, Sevastova lost the opening game of the third set before steamrolling Pegula the rest of the way.

Pegula was perplexed over her collapse.

'It was a strange match for me,' Pegula said. 'I felt like I was in complete control, and then I played a couple of terrible games.'

Sevastova was ranked as high as No. 11 in 2018 before injuries hampered her career. She was ranked No. 396 entering Friday's match.

In 2018, Sevastova advanced to the U.S. Open semifinals before losing to eventual runner-up Serena Williams.

She will next face the winner of that 2018 U.S. Open -- Naomi Osaka.

Osaka, a former No. 1 player, moved into the fourth round with a 6-2, 6-4 victory over No. 22 Jalena Ostapenko of Latvia.

Osaka of Japan had five aces and converted 6 of 9 break-point opportunities.

Ostapenko trailed 3-1 in the second set when she attempted to rally. She moved within one game before Osaka closed it out.

No. 6 Madison Keys struggled early before recovering for a 2-6, 6-3, 6-3 victory over Catherine McNally.

No. 16 seed Clara Tauson of Switzerland notched a 6-3, 6-0 triumph over Yuliia Starodubtseva.

No. 2 seed Iga Swiatek of Poland plays Germany's Eva Lys on Friday night.

--Field Level Media