RIYADH, Saudi Arabia -- World No.3 Coco Gauff joined No.2 Iga Swiatek atop the Orange Group after defeating No.6 Jessica Pegula 6-3, 6-2 in her opening match at the WTA Finals Riyadh presented by PIF. The victory is Gauff's 20th career Top 10 win and first on hard court since last year's WTA Finals in Cancun.

Gauff will face Swiatek on Tuesday, with the winner taking control of the Orange Group. Pegula will face Wimbledon champion Barbora Krejcikova.

WTA Finals Riyadh: Scores | Schedule | Standings

Gauff came into her opening match against Pegula as the favorite by ranking and form, but an underdog based on history. Pegula won four of their five previous meetings, including their past three. Both Americans have enjoyed a surge in the back half of the season. Pegula tore through the North American hard-court season with a title in Toronto and back-to-back finals in Cincinnati and the US Open. 

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But Gauff ran through the tape in the regular season, winning the China Open to win her second WTA 1000 title and making the semifinals in Wuhan the following week. That run sealed the 20-year-old's spot in her third straight WTA Finals. Since the reintroduction of the round-robin format in 2003, she is only the second player to reach three or more consecutive WTA Finals before the age of 21, joining Maria Sharapova (2004-07). 

"I think maybe I served better than previous times and this is our first time, I think, playing each other on indoor hard, so maybe that had something to do with it," Gauff said.

"I don't know. I think I know I've lost to her a lot, but it doesn't feel like it sometimes, because we do practice a lot, and obviously when we're playing sometimes I win practice sets, sometimes she does. So it doesn't feel like the head to head is as bad as it was."

In quicker conditions that would seem to favor Pegula, Gauff was the one who proved more effective off the ground. She doubled-up Pegula in the winners column, striking 16 to Pegula's eight, and kept more sustained pressure on Pegula's serve. Gauff generated eight break-point chances over the 75-minute match and converted five. Pegula could only manage two breaks from three chances.

"I just felt kind of off," Pegula said. "I didn't feel like I was necessarily hitting the ball that bad, but just making a couple extra errors. Against someone like that, who's obviously had a really good fall after the Open too, she's feeling confident, so you just can't really let those moments kind of slip away."

"I thought we both were playing high level," Gauff said. "I just think I was able to break through on the more important points."

Next up for Gauff is a 13th career meeting against Swiatek. The Polish player came from a set and a break down to defeat Krejcikova in her opener to secure her first victory since the US Open. Swiatek holds a domineering 11-1 head-to-head record against Gauff. 

Pegula will look to bounce back against Krejcikova. It will be their first meeting since 2023 Dubai. They have split their two prior meetings. 

"I've been playing well all week, so I know that it's there," Pegula said. "I just need to kind of put my head down, look forward to the next match and really try and I think, kind of get some more energy the next match. I just felt a little flat today."