Cancun (Mexico) World No.2 Iga Swiatek and No.3 Coco Gauff secured their spots in the semifinals of the WTA Finals, finishing in the top two of the Chetumal Group after winning their respective matches.
Gauff won a battle of two of the Grand Slam champions from this season, defeating Marketa Vondrousova 5-7, 6-7(4), 6-3 in the final round of group play on Friday night, the first teenager to make the final four of the year-end championships since Caroline Wozniacki in 2009.
Later in the evening, Swiatek confirmed her position as the group winner after defeating No.6 seed Ons Jabeur 6-1, 6-2 to go 3-0 in the Chetumal Group.
On Saturday, Swiatek will face No.1 Aryna Sabalenka in a match that could decide the year-end No.1 ranking. If Sabalenka wins, she will finish the year at No.1. If Swiatek prevails, she can retake the top spot only by winning the title, WTA reports.
This is a rematch of last year's semifinal in Fort Worth, where Sabalenka won 6-2, 2-6, 6-1. The two have split their two meetings this season, both on clay. Swiatek won the Stuttgart final, while Sabalenka took Madrid.
The other semifinal will showcase Gauff against No.5 Jessica Pegula. It will be the first all-American semifinal at the WTA Finals since the reintroduction of the round-robin format in 2003.
Both players are making their semifinal debuts at the year-end tournament. Last year in Fort Worth the duo went winless in both singles and doubles. This will be the third meeting of the year between the two top-ranked Americans. Gauff won on the grass in Eastbourne and Pegula got her revenge during her title run in Montreal this summer.
Friday's victory was Gauff's 51st of the season. She is the first American teenager to register 50 or more wins in a single season since Venus Williams in 1999.