NEW YORK (AP) — Despite recent efforts to fix her unreliable serve, Coco Gauff’s opening match at the U.S. Open got off to a shaky start Tuesday night. She opened with a double-fault — one of 10 in the match — and was broken in her first service game. By the end of the night, she had been broken six times.

But the only numbers that mattered were those on the Arthur Ashe Stadium scoreboard: a hard-fought 6–4, 6–7(2), 7–5 victory over Ajla Tomljanovic, sending the No. 3 seed into the second round at Flushing Meadows.

“It wasn’t the best,” Gauff admitted, “but I’m happy to get through.”

Nothing came easy. Gauff twice held a break advantage in the second set but couldn’t close it out. Up 5–3 in the third, she served for the match at 5–4 but faltered with back-to-back double faults and two forehand errors, letting Tomljanovic level at 5–5.

Rather than fold, Gauff regrouped, broke back immediately, and finally sealed the win on her second opportunity — nearly three hours after the match began.

“I had so many chances… I was just like, ‘Eventually, one of these is going to go my way,’” she said.

Gauff, who won her first major here last year as a teenager, recently added biomechanics expert Gavin MacMillan to her team. MacMillan, who helped current No. 1 Aryna Sabalenka revamp her serve, sat in the front row of Gauff’s box, right beside her mother.

After the match, Gauff described their training sessions as “really tough” and “mentally exhausting.”

“I’m trying to improve with each match,” she said.

Gauff entered the U.S. Open with a tour-high 320 double faults this season — more than 100 above any other player. She hit 23 in one match earlier this month, and 14 in the next.

On Tuesday, she began cautiously, serving slower than usual as she worked through her adjusted motion. But as the match intensified, so did her serve: her average first-serve speed climbed from 88 mph in the first set to 97 in the second, and 101 in the third after the roof closed. She fired one serve at 117 mph and even hit a second-serve ace.

What ultimately carried her past Tomljanovic — best known for ending Serena Williams’ career here in 2022 — was her elite movement, aggressive backhand, and net play. She won 12 of 15 points at the net, including a spectacular leaping back-to-the-net volley in the third set.

Appropriately, she converted match point with a clean backhand winner down the line, then waved her arms to energize the crowd.

The win marks Gauff’s first Grand Slam match since a first-round exit at Wimbledon in July, which followed her French Open title in June.

Now, as she continues her U.S. Open run, Gauff has a chance to climb to World No. 1 for the first time — potentially overtaking both Aryna Sabalenka and Iga Świątek.