Sakkari saved 14 of 15 break points on the night to outclass her determined opponent and will join Iga Swiatek, Ons Jabeur, Jessica Pegula, Coco Gauff, Caroline Garcia, Aryna Sabalenka and Daria Kasatkina at the season finale.

"Without fire you cannot win these matches," said Sakkari, whose victory denied her opponent a debut singles appearance at the tournament.

"Without heart, without courage, without going for it and being brave you cannot get these opportunities, you cannot win them."

The WTA Finals, featuring the world's top eight singles players and doubles teams, will start in Fort Worth, Texas on Oct. 31.

Earlier, experience triumphed over youth as twice major winner Victoria Azarenka (33) beat American Gauff (18) 7-6(2) 4-6 6-3 to stay on track to end a two-year title drought.

Azarenka kept her poise under a barrage of powerful serves as the world number seven lobbed 10 aces across the net. She broke down Gauff's stout defence to convert on 5 of 13 break point chances and set up a meeting with Jessica Pegula of the United States.

"She served really well, she was mixing a lot so I was trying to adjust," Azarenka said. "I tried to just stay consistent."

Gauff, who reached her first Grand Slam final at Roland Garros earlier this year, had already booked her spot at the WTA Finals and the last qualification spot will be decided in a face off on Friday between Maria Sakkari and Veronika Kudermetova.

"She's the same age as my career so it felt pretty interesting," said Azarenka. "She's such a great athlete, I can't wait to see how far she can go."

Pegula has been playing the best tennis of her career in 2022 and showed no signs of losing that momentum Friday when she rolled over compatriot Sloane Stephens 6-2 6-2.

The quarter-finalist at the Australian Open, Roland Garros, and US Open set the tone when she broke Stephens immediately to open the first set and dropped only three of her first-serve points in the second frame.