Coco Gauff kicked off her WTA Finals campaign with a commanding 6-3, 6-2 victory over fellow American Jessica Pegula on Sunday.
Second-seeded Iga Swiatek, making her return after a two-month hiatus, fought back to defeat Barbora Krejcikova 4-6, 7-5, 6-2.
Gauff showcased her skills by converting five of her eight break-point chances, marking a strong start at the prestigious year-ending tournament featuring 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."
Gauff will face Swiatek on Tuesday, with the winner taking control of the Orange Group. Pegula will next face Wimbledon champion Krejcikova.
Swiatek, who arrived at the WTA Finals with a new coach, hadn’t played a match since losing to Pegula in straight sets in the U.S. Open quarterfinals in September.
"Even though I played a lot of those (practice) matches, I kind of forgot for a while how it feels to experience all those things – a bit of 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 rallied from 3-0 down in the second set to turn it around against Krejcikova, who has been hampered by injuries and had played only 29 matches coming into the finals, seven of which were victories at Wimbledon.
On Saturday, top-ranked Aryna Sabalenka eased to a straight-set victory over Zheng Qinwen in the opening match of the finals in Saudi Arabia. Fourth-seeded Jasmine Paolini of Italy defeated fifth-seeded Elena Rybakina in the other Purple Group match.
