World No. 1 Iga Swiatek qualified for the semi-finals at the WTA Finals here in Texas on Thursday after Daria Kasatkina beat American Coco Gauff 7-6(6), 6-3 in a round-robin stage match at the eight-player, season-ending tournament. Swiatek, who improved to 2-0 in this year’s competition following her own 6-3, 6-2 win over Caroline Garcia, goes through as the winner of her group.

Gauff, who started the match strongly, can no longer qualify for the semi-finals. The American teenager had taken a 4-1 lead before Kasatkina fought back to level the first set at 5-5. Gauff’s eyes welled up with tears during the changeover after she was then broken to fall behind 5-6.

The 18-year-old regrouped to force a tie-break, but Kasatkina once again showed grit to fight back and claim it 8-6. WTA Finals debutante Kasatkina kept up the pressure in the second set and eventually served out the match. “To win for the first time at the Finals is an incredible feeling,” Kasatkina said. “I hope I can make it (to the semi-finals) in the next match.”

For Swiatek, who upped her career grand slam tally to three, her victory over Garcia earlier on Thursday gave her some measure of revenge on the Frenchwoman after having fallen to her in the quarter-final at the Poland Open in July. The 21-year-old Pole broke at love for a 5-3 lead and then served out what proved to be a tight opening frame on her third set point when world No.6 Garcia sent a forehand long. Swiatek then broke Garcia to start the second set and in the next game calmly roared back from 0-40 down to hold serve and never faced a break point the rest of the way in a match she sealed in style with an ace.

“She was putting a lot of pressure and putting a lot of speed on her balls so I needed to get them back and hit them even better. I was ready for that,” Swiatek said later.