FORT WORTH, Texas -- Ons Jabeur wasn't used to the idea of playing so soon after a loss in her WTA Finals debut.
Took her a bit to adjust as well.
The Tunisian rallied for a three-set victory over Jessica Pegula on Wednesday night, keeping alive the US Open finalist's hopes of advancing out of group play in the season-ending event.
Jabeur won the last three games in each of the second and third sets in her 1-6, 6-3, 6-3 victory after dropping seven consecutive games early in the match.
A loss would have eliminated the 28-year-old Jabeur from the semifinals because Maria Sakkari beat Aryna Sabalenka 6-2, 6-4 in the late match in a meeting of players who won their openers in the round-robin format.
Sakkari clinched one of the two spots in the semifinals from her group.
Jabeur won the first set two nights earlier against Sabalenka and got within two points of winning before the No. 2-ranked player faltered on the indoor hard court at Dickies Arena.
"It was tough because I'm used to just be depressed for the next two days when I lose," said Jabeur, the first Tunisian to win a WTA Finals match. "I didn't have much time here, and it was very tough to sleep the first day to be honest with you."
It was just the second win in the past nine matches against a top-10 opponent for Jabeur, who also beat Pegula in the Madrid final on clay in May.
No. 3 Pegula, another first-time WTA Finals participant who was set to play doubles with fellow American Coco Gauff in the final match of the day, has lost nine in a row against top five foes.
Pegula temporarily kept alive her hopes for the semifinals by winning a set, but is a long shot after falling to 0-2 in the tournament.
The event was moved to Texas from China because of concerns about the safety of Peng Shuai, a Grand Slam doubles champion who accused a former government official there of sexual assault.
Coronavirus restrictions also played a part, and WTA Tour Chairman and CEO Steve Simon hopes the event can return to China.
Jabeur, the first African woman to reach the WTA Finals since Amanda Coetzer in 2001, rallied from love-40 to hold in a five-deuce first game of the third set, then Pegula saved two break points to get even at 3-3.
Pegula couldn't do it again, losing at love on her serve to give Jabeur the chance to close out the match.
After dropping the first game of the match, Pegula won seven in a row for a 1-0 lead in the second set before Jabeur, who had 11 unforced errors in the first set, held serve.
"She was playing really well, and she was playing very fast," Jabeur said. "I just had to find that click to change up the rhythm and impose my game more than her game."
No. 5 Sakkari beat Sabalenko in the WTA Finals for the second consecutive year, needing an hour and 37 minutes after a nearly three-hour match that included two tiebreakers a year ago.
Two of Sakkari's three victories against top 10 players have come this week after she won tiebreakers in both sets to beat Pegula.
"It's been a long time since I had straight-set wins against these players,'' said Sakkari, who is in the WTA Finals semifinals for the second consecutive year. "That's something new again for me. But at the same time, I'm being more clinical, and I can be even more.''
Defending doubles champions Barbora Krejcikova and Katerina Siniakova beat China's Yifan Xu and Zhaoxuan Yang 6-3, 6-3, putting the Czech duo in the semifinals.
American Desirae Krawczyk and Demi Schuurs of the Netherlands beat Pegula and Gauff 3-6, 6-0, 10-5 in a champions tiebreaker.