On Sunday, Aryna Sabalenka defeated world number one Iga Swiatek 6-2, 2-6, 6-1 to set up a title match against Caroline Garcia at the season-ending WTA Finals.
Sabalenka avenged a three-set loss against Swiatek of Poland in the US Open semi-finals, when Swiatek went on to win her second Grand Slam title of the year after winning Roland Garros.
Swiatek, who won eight singles titles this season, had her 15-match winning streak against top-10 players come to an end.
Her usually ferocious forehand was unexpectedly unreliable, as she hit 26 wins and 26 unforced mistakes.
Swiatek had only been broken once in her three round-robin matches, but Sabalenka broke her three times in the first set on Sunday.
Swiatek appeared to have re-set, surging to a 4-0 lead in the second but Sabalenka held off a break point to win 4-1. Sabalenka broke to trim the lead to 4-2, but Swiatek quickly reclaimed the break and served it out to tie the match at one set apiece.
Sabalenka took an early break in the third set, as she did in their previous meeting at the US Open.
This time, though, she was able to hold on to her lead, breaking again for a 5-1 lead and finishing with an ace and a service winner.
Sabalenka and Garcia will restart their battle on Monday, which they have split four times 2-2.
Garcia, who has three titles this season and has risen to the top of the rankings, put on a clinic against Sakkari, winning in 75 minutes.