Coco Gauff and Caroline Garcia qualified for the eight-player WTA Finals after Aryna Sabalenka lost to Liudmila Samsonova in the Guadalajara Open second round in Mexico on Wednesday.

Russian Samsonova, who has won 20 of her last 22 matches, smacked 21 winners and broke the powerful Belarusian four times en route to a 6-4 2-6 6-2 upset win over the world No. 4.

The WTA Finals featuring the world's top eight players starts in Fort Worth on October 31. 

Iga Swiatek, Ons Jabeur and Jessica Pegula had already locked up the first three spots before Guadalajara so with the addition of American Gauff and France's Garcia, three openings remain. 

Fifth seed Gauff was not at her best but was still good enough to see off Italy's Elisabetta Cocciaretto 7-6(1) 6-3.

"I'm just super excited," said Gauff, 18, who will be the youngest player to compete at the WTA Finals since 2005.

"I wasn't really thinking about it before the match, but I'm excited to join Jess (Pegula)," she said. The pair have also both qualified for the WTA Finals doubles tournament. 

Wimbledon champion Elena Rybakina's hopes of making the Finals ended after Pegula saved three match points to emerge with a 2-6 6-3 7-6(8) victory despite 14 aces from the Kazakhstani. 

Rybakina would have qualified for the Finals if the WTA had issued ranking points at this year's grass court major. 

Danielle Collins and Jelena Ostapenko, who both have an outside shot of making the WTA Finals, won their second round matches on Wednesday, while other hopefuls including Madison Keys, Belinda Bencic and top seed Paula Badosa play later.

In the men's field, Novak Djokovic, Rafael Nadal, Carlos Alcaraz, Casper Ruud and Stefanos Tsitsipas already qualified for the ATP Finals, which takes place from November 13 to 20, with former World No. 1 Daniil Medvedev leading the contenders for three other places at the season finale.

(With input from Reuters)