Coco Gauff beat Marta Kostyuk 6-4, 7-5 in Group 1 of the WTA Finals in Indian Wells on Thursday, winning the last six games of the match after trailing 5-1 in the second set. The American, who took a medical timeout for her back, now needs Linda Noskova to beat Jessica Pegula later on Thursday to reach the semi-finals.

From 5-1 down to six games in a row

Gauff took the first set after moving from 2-1 to 5-2, before Kostyuk won two games in a row to make it 5-4. The American closed it out 6-4.

The second set turned the other way. Kostyuk raced to a 4-0 lead and Gauff, who called the trainer for her back, looked in trouble when she trailed 5-1. But the Ukrainian lost her way completely from there. Gauff won six games in a row to close out the match in 1 hour 40 minutes.

Gauff now leads their head-to-head 5-2. Kostyuk, the alternate who replaced defending champion Elena Rybakina, ends her week without a win and has now lost seven matches in a row.

Gauff needs Noskova to beat Pegula

Noskova has already clinched her semi-final spot. If she beats Pegula, Gauff goes through as group runner-up. If Pegula wins, the American takes the second place. Noskova has won three of their four meetings, including the Berlin final, 6-4, 4-6, 6-3.

Gauff, the 2024 champion, is chasing her third semi-final at the WTA Finals. The semi-finals are on Saturday.