Iga Swiatek said she was pleased with her "solid" start to the WTA Finals after the world No 1 eased past Russia's Daria Kasatkina in straight sets on Tuesday.
Swiatek, who has enjoyed a stellar year which included Grand Slam titles at Roland Garros and the US Open, claimed a 6-2, 6-3 victory in 1hr 22min at Fort Worth's Dickies Arena in Texas.
The 21-year-old Pole is the heavy favourite to add to her tally of eight tournament victories at this week's eight-player tournament.
Against Kasatkina, the world No 8, the three-time major champion was quickly into her stride, racing to a 3-0 lead after an early break of serve. Swiatek wrapped up the first set in just 37 minutes after securing another break of serve in the eighth game.
The second set followed a similar pattern as Swiatek grabbed an early break to take control for a 3-0 lead before closing out the set.
Swiatek is aiming to atone for her disappointing display at last year's finals, held in Guadalajara, when she failed to qualify for the semi-finals.
"I'm pretty happy that I could start so solid," Swiatek said of her win. "I feel like it gave me confidence throughout the whole match.
"I knew it was gonna be hard to balance being aggressive and you know, not making a lot of mistakes, because she can really reset the rallies."
Swiatek said working to improve her service game had been the key to her season of success.
"I felt like sometimes last year, my serve was letting me down," she said. "And this season I can lean on it. Maybe it's not like I'm serving aces, but I feel more solid."
Garcia defeats Gauff
In Tuesday's other Group Tracy Austin match, France's sixth-seed Caroline Garcia defeated fourth seed Coco Gauff in a repeat of their US Open quarter-final in September.
Garcia, who reached the semi-finals at Flushing Meadows before losing to Tunisia's Ons Jabeur, took 1hr 18min to defeat US hope Gauff 6-4, 6-3.
“The past couple of years have been very rough,” said Garcia, at 29 the oldest player in the field at Fort Worth. “I’m really, really happy to be back. Five years is quite a long time in a career, but you try to manage as best you can.”
Garcia is also the only player at the WTA Finals who has defeated Swiatek this year, doing so in front of a partisan crowd at the Poland Open in July.
“It’s definitely a good experience to take,” Garcia said. “To be aggressive is probably the best to try to beat her. When she has time to do her things, it’s very complicated. She changes direction so well. She moves very well on court; with her sliding, she looks like she covers two courts.”
The tournament features two groups of four players who play in a round-robin format, with the top two in each group advancing to the semi-finals.
Group Nancy Richey players return to the court on Wednesday as Jabeur, aiming to bounce back from her defeat to Aryna Sabalenka, takes on Jessica Pegula while Sabalenka faces Maria Sakkari.