FORT WORTH, Texas — Maria Sakkari couldn’t help but smile a wide smile after taking a pair of tiebreakers to edge Jessica Pegula across more than two hours of big-hitting baseline action in front of a sparse crowd Monday as round-robin singles play began at the WTA Finals.

Sure, the No.5-ranked Sakkari was excited about the 7-6 (6), 7-6 (4) victory on a temporary indoor hard court at Dickies Arena against No. 3 Pegula in the season-ending tournament, just eight days after losing to the American in the final of another event.

For Sakkari, who will face Aryna Sabalenka next, this was of more importance: She got to hang out with her parents and grandmother — the first time in 4 1/2 years her mom’s mom had been in the stands to see the 27-year-old from Greece compete.

“She was like, ‘Wow. That was a very high-level match.’ She knows tennis really well, because my grandfather was a coach, then my mom was a player, so she traveled with her on the tour. It’s not like she’s watching her first tennis match ever,” a beaming Sakkari said. “It’s very nice just to have her around. To be with her. To spend my time a little bit with her and my parents. It’s nice, sometimes, to (be with) people that you love and people that are very close to you and were (there) since the beginning.”

Grandma hadn’t been on hand for one of Sakkari’s matches since she lost to Kiki Bertens in the first round of the Madrid Open in May 2018.

“Nice to have here, for sure — and see me winning,” Sakkari said.

Later on Day 1, Sabalenka came back to beat two-time Grand Slam runner-up Ons Jabeur 3-6, 7-6 (5), 7-5 after being two points from defeat. The No. 2-ranked Jabeur led 5-3 in the tiebreaker, but Sabalenka grabbed the next four points in a row to force a third set.

“Don’t look at the score,” Sabalenka said she told herself. “Just keep trying.”

A resigned Jabeur, who meets Pegula on Wednesday in the round-robin format, said afterward: “I missed my chances.”

In the match that closed out Monday’s schedule, Pegula and Coco Gauff were beaten in doubles by Xu Yifan and Yang Zhaoxuan 6-4, 4-6, 10-7 in a champion’s tiebreaker that wrapped up a little past midnight. In the day’s other doubles match, defending champions Barbora Krejcikova and Katerina Siniakova defeated Desirae Krawczyk and Demi Schuurs 6-4, 6-3.

On Oct. 23, in the final of the Guadalajara Open, Pegula beat Sakkari 6-2, 6-3 to claim the first WTA 1000 title of her career.

“It’s never easy against Jess,” said Sakkari, who was a two-time Grand Slam semifinalist last season but only once made it as far as the fourth round at a major in 2022.

That was part of why Sakkari has described going through what she termed a “dark phase,” one she snapped out of by reminding herself that she is still a top player.

This rematch against Pegula was filled with plenty of momentum swings.

Sakkari won the first two games. Pegula took the next three. Sakkari broke to lead 6-5 and serve for the first set. Pegula broke right back when Sakkari flubbed a drop shot, then chucked a ball and walked over to a towel holder and gave it a kick.

The second set followed a similar pattern. Sakkari led 3-0. Soon, it was 3-all.

Sakkari had an opportunity to close out her first win against a top-five opponent this year when she held two match points at 6-5 in second. But she dropped a backhand into the net on the first, and Pegula delivered a backhand winner on the second.

“Maybe I was a little bit too passive,” Sakkari said.

In the second tiebreaker, she said she realized she needed to be more aggressive, “because I felt like if you’re passive, then the ball does nothing” on the slow court.

Sakkari converted her third match point on a forehand into the net by Pegula, who had won 11 of her preceding 13 matches — with both losses to No. 1-ranked Iga Swiatek.