Coco Gauff started strong by defeating Jessica Pegula 6-3, 6-2 in their match at the WTA Finals on Sunday. Meanwhile, second-seeded Iga Swiatek overcame Barbora Krejcikova 4-6, 7-5, 6-2 in her return match after a two-month break.
Gauff capitalized on five out of eight break-point chances to secure the victory in the year-ending tournament for the top eight ranked players.
"I thought we both were playing at a high level," Gauff said. "I just think I was able to break through on the more important points."
Next, Gauff will play against Swiatek on Tuesday, a match that could determine the leader of the Orange Group. Pegula will face Wimbledon champion Krejcikova.
Swiatek, who recently started working with a new coach, had not played since losing to Pegula in the US Open quarterfinals in September.
"Even though I played a lot of those (practice) matches, I kind of forgot for a while how it is to feel all those things, a bit different stress and emotions," Swiatek said. "For sure, I needed some time to adapt. The most important thing was that even though it happened, I managed to fight through that. And was patient enough to wait to get better."
Swiatek recovered from a 3-0 deficit in the second set to win against Krejcikova, who had battled injuries and could only play 29 matches this year, with seven wins at Wimbledon.
