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 during the match. 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 w