Coco Gauff clawed out a 6-4, 7-5 round-robin victory over Marta Kostyuk on Thursday to stay alive in the WTA Finals in Indian Wells, California.

If fifth-ranked compatriot Jessica Pegula beats Wimbledon champion Linda Noskova in the last group one match later Thursday Pegula will go through instead. Noskova has already advanced.

But Gauff did what she could with a gutsy straight-sets win. Trailing 5-1 in the second set she saved three set points in the seventh game to launch a run of six straight games to seize the match.

The first set had also been a battle. Broken in the opening game, Gauff appeared to have seized control when she broke Kostyuk for a second time for a 4-2 lead then held for 5-2.

But after having the wrist taped she came back to hold serve then broke Gauff as the American served for the set -- Gauff helping her out with a pair of double faults.

Gauff regrouped to take the set, but she was soon struggling and after going down two breaks to trail 3-0 in the second she received treatment for what she later said was back tightness.

Despite nine double faults, however, Gauff prevailed in one hour and 39 minutes.

"I'm not going to lie, (my) head was already in that third set," Gauff said of her mindset trailing 5-1.

"Then once it got to 5-4 I was like, 'OK, I can win this set.' I got a little bit lucky. She gave me a few errors. I'm glad I was able to close that out."