Iga Swiatek beat an out-of-sorts Coco Gauff 6-0, 6-4 in windy conditions at the WTA Finals in Cancun on Wednesday while Ons Jabeur avenged her Wimbledon final loss by besting Marketa Vondrousova 6-4, 6-3, blowing the race to the semis wide open.
Swiatek came out firing in their group stage match and broke the US Open champion for a second time with a lovely looping crosscourt winner to take a 4-0 lead.
Two games later, the second-seeded Pole pounced on a poor drop shot from the American teenager and blasted a backhand past her to capture the one-sided first set.
Gauff raised her level early in the second, winning three straight games for a 3-1 advantage and coming out on top of a marathon service game 4-2.
But the four-time major champion would not back down, holding at love and then breaking back on Gauff's badly missed forehand into the net for 4-4.
From there Gauff began to unravel.
She threw her racket against the court in frustration after four straight double faults while serving for the set at 5-4 and appeared on the verge of tears in the next game, where she whiffed on a return of serve en route to a love hold.
Swiatek improved her lifetime tally to 9-1 against Gauff when the third seed's overhead landed in the net on match for her 31st unforced error of the contest.
The evening group stage match saw a rematch of the Wimbledon final as sixth seed Ons Jabeur got back at the Grand Slam winner Vondrousova with a straight set win.
The first set had a competitive start with both players locked 2-2, until Jabeur swung the momentum in her favour by breaking Vondrousova's serve.
The former world No. 2 took just short of an hour to win the first set and about half that to clinch the second, ending her three-match losing streak against Vondrousova with a commanding victory.
It was Jabeur's first win in the group after Monday's loss to Gauff, leaving both of them with one win each as Swiatek holds the top spot with two victories.
Vondrousova is at the bottom after two losses in the group.
All four players in the group can reach the semifinals as Friday's fixtures pit Swiatek against Jabeur and Gauff against Vondrousova in the last round of the group stage.
