Coco Gauff storms back from 5-1 down to beat Marta Kostyuk at the WTA Finals

Coco Gauff rallied to win the final six games of the match and beat Marta Kostyuk 6-4, 7-5 in her round-robin group at the WTA Finals on Thursday.

Then came more suspense.

Gauff's eventual fate depended on the outcome of fellow American Jessica Pegula's match against Wimbledon champion Linda Noskova later. A victory by Pegula would knock Gauff, her former doubles partner, out and advance Pegula to the semifinals of the season-ending championships. Gauff beat Pegula in three sets in their opening Group 1 match.

Noskova had already advanced to the semifinals at the $10 million event in the Southern California desert, which was moved from Saudi Arabia because of the Iran war in the Middle East.

Gauff overcame serving issues and visits from a trainer to massage her back during the match. It initially stiffened up in her first match and bothers her on serves and forehands. She received a painkiller.

"I think it's kicking in now,” she said, laughing afterward, “so I feel good.”

Kostyuk raced to a 4-0 lead in in the second set, fighting off four break points to hold in the second game. Twice, Gauff double-faulted away games. She requested a trainer early in the set to work on her as she lay on her side while Kostyuk walked over to sit on the advertising board and chat with her team.

“I was just preparing to play a third (set) at that point,” Gauff said.

Kostyuk led 5-1 before Gauff's comeback began. She fought off three break points and hit a crosscourt forehand winner to trail 5-2.

Kostyuk's wrist began hurting in the first set and a trained tended to it.

“I couldn't really serve anymore,” she said. “I couldn't even hit the ball properly anymore, so I started to miss a lot. I was like, ‘I have to finish this match because it’s just not fair, like for everyone, if I would just stop here right now.'"

Gauff broke twice to tie the set at 5-5. Gauff held for a 6-5 lead and won the match on Kostyuk's netted forehand.

“One game turned into another and I think she got a little bit frustrated too, so that kind of helped me," Gauff said. "Once it was 5-all, I felt momentum was on my side and I just needed to keep my foot on the gas.”

Gauff led 5-2 in the first set before Kostyuk broke to close to 5-4. Gauff broke back in the next game with a gutsy crosscourt backhand volley winner to take the set.

Kostyuk got into the Finals as the first alternate after top-ranked Elena Rybakina withdrew because of a viral illness. The 24-year-old Ukrainian went 0-3 in Group 1 play.

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