Pakistan, Nov. 14 -- Jessica Pegula isn't known as one of the WTA Tour's big servers. Turns out deceptively mixing types of serves - kick, hard, flat - can be enough of a weapon to set up her baseline game.

Pegula fired a career-high 16 aces and saved a match point before winning the final three games to beat Linda Noskova 7-6 (2), 4-6, 7-5 in her round-robin group at the WTA Finals on Thursday. The victory moved the American into the semifinals to face Mirra Andreeva.

"Even with 16 aces, it just goes to show how good of a player she is because I was still barely able to win the match," Pegula said. "I tried to keep her guessing a little bit on the serve. I think that's why I got some free points there."

Noskova had already advanced to...