Top-ranked Aryna Sabalenka put on a dominant serving display in her opening match at the WTA finals, producing 10 aces in a 6-3 6-1 win over No 8-ranked Jasmine Paolini on Sunday.

Sabalenka served four aces in the final game of the first set alone and overall put 82.7 per cent of her first serves in play.
The match, which was Sabalenka's 500th at the WTA level, lasted 70 minutes.

"I was focused, I was calm and it felt like everything was in control," Sabalenka said.

"I'm super happy and super proud of the work that has been done and that things are working and I'm getting better and better every day. And I just hope that we're going to keep doing what we're doing and hopefully we can stay there."

The season-ending tournament for the year's top eight players starts with two four-woman groups of round-robin play. The top two finishers in each group advance to the semi-finals.

"I take this tournament as a regular tournament that I have to win five matches if I want to win the title," Sabalenka said. "So I'm just trying to bring my best tennis and fight for every point."

Iga Swiatek and Elena Rybakina won their opening matches on Saturday.

In the same group as Sabalenka, Jessica Pegula beat defending champion Coco Gauff 6-3 6-7 (4-7) 6-2 in an all-American matchup.

Gauff again struggled with her serve, hitting 12 double-faults - including one to hand the first set to Pegula, her former doubles partner.

Before she ultimately pulled it out in the tiebreaker, Gauff twice failed to serve out the second set. On her second such chance, she hit three consecutive double-faults to let Pegula break her again and force a tiebreaker.

Three weeks ago, Gauff beat Pegula in the final of the Wuhan Open in China.

"Coco is a great champion, great competitor, good friend. So it's always tough playing her," Pegula said. "I don't think there's any secrets with this group of girls here."

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