Coco Gauff's serve, a source of significant struggle at last year's US Open, has undergone a dramatic transformation, now serving as a key weapon in her game. This revitalized serve was on full display during her first-round match at this year's tournament, where she defeated Zeynep Sönmez.

Gauff's improved accuracy and maintained power have been evident since her Cincinnati Open title win earlier this month. Analysis from that tournament indicated that Gauff is striking the ball closer to the service line while sustaining her serve speed, a significant enhancement in her precision. This newfound confidence in her serve's effectiveness was immediately apparent against Sönmez.

In the opening game, Gauff delivered a 112 mph ace down the middle, followed by an unreturned first serve and another ace, securing her service game in under 90 seconds. In the first set, Sönmez found it difficult to return Gauff's serves, with the world number four winning 93% of points when landing her first serve in play.

While Gauff secured a break for a 1-0 lead in the second set, her serve became less dominant, allowing Sönmez to level the score at 2-2 and later hold three break points for a 4-2 advantage. However, Gauff managed to hold serve, aided by a precise out-wide ace and a 115 mph unreturned first serve – a game she acknowledged she likely would have lost a year ago.

This crucial hold provided the foundation for Gauff to immediately break for a 4-3 lead. She then clinched the victory with another service game that underscored her renewed belief. Gauff hit three unreturned first serves, all just under 120 mph, creating three match points. Sönmez faltered on the first, succumbing after a short rally.

"Psychologically, I'm now going to go for the ace, or I know I can hit the serve and the return is probably not going to come back," Gauff stated. "Last year I literally was like I hope I make it in. It's such a big difference knowing almost every serve I'm trying to basically hit 110, 115, 120mph if I can."

Gauff is set to play either Paula Badosa of Spain or Daria Saville of Australia in the second round.