MELBOURNE, Australia — Coco Gauff threw away her forehand and serve in the worst possible way and at the worst possible time at the Australian Open. The unforced errors piled up, as did the double faults and break points, often followed by palms to the eyes or slaps on the thighs.

All in all, Goff's trip to Melbourne Park and her 13-game winning streak dating back to the end of last season finally came to an end in the quarter-finals. The 2023 U.S. Open champion was unable to control the match on a hot afternoon at Rod Laver Arena and was eliminated by Spanish No. 11 Paola Badosa 7-5, 6-4.

After failing to defend his title in New York in September, the 20-year-old Gauff made some key shot adjustments and changed his coaching staff, arriving in Australia with hopes of winning a second Grand Slam title.

"I feel like (at) the U.S. Open, I didn't find a solution, so that's more frustrating," Goff said. "Today, I felt like I was working on a solution; I knew what I needed to do. The U.S. Open, I needed to work on my serve. Not that my serve was where I wanted it to be, but I worked on it and it was obviously A big improvement, so I want to keep working hard and keep playing hard.”

Goff added: "So I feel like I'm on the right path. Even though I lost today, I feel like I'm on an upward trajectory."

The American enters Tuesday with a 9-0 record in 2025; she also won her final four matches last season and captured the trophy at the WTA Finals in November.

"There's still a lot of work to be done," Gauff said after losing in one hour and 43 minutes to Badosa, who won 0-2 in the Grand Slam quarterfinals. "I'm obviously disappointed but I'm not completely devastated

Badosa is now playing in her first Grand Slam semifinal at the age of 27, less than a year after she considered retirement because of a stress fracture in her back that took a long time to heal and initially failed to respond to a cortisone shot.

"I wanted to (give) one last try," Badosa said, "OK, here I am. So I'm really proud of everything that we and my team have been through, especially how I've (battled) through it." All this, especially mentally.”

In May 2023, shortly after she started working with coach Paul Toledo, she was injured while practicing for the tournament in Rome. A year later, including a few months after the tour ended, the problems remained.

"The reality is the back is not responding. We can't find a solution. Paola is frustrated," Toledo said. "I was like: This isn't going to work. I don't know what we have to do."

With a new doctor, fitness trainer, and nutritionist, Badosa tried different exercises and supplements, and her back improved.

"The puzzle," she said, "is starting to look better."

On Tuesday, she kept the pressure on Gauff, who ended up committing 41 unforced errors, including six double faults and 28 forehand errors. Badosa earned a total of 10 break points and won four of Gauff's service games. Gauff, meanwhile, had never had so many break points before losing a set and breaking serve.

A crucial game - and one that was illustrative of Gauff's problems this afternoon - began the second set. The game lasted for more than ten minutes, with the point difference reaching 22 points. After Gauff missed two consecutive forehands, Badosa seized the fifth break opportunity.

Badosa scored 12 points in that game, 11 of which came from Gauff's mistakes, including seven forehand errors.

"Today," Goff said, "she was better in those clutch moments."

When Badosa hit a forehand winner to end her quarterfinal match, she covered her mouth with her hands, then dropped to her knees and lowered her head. It's a big moment for someone who reached a career-best No. 2 ranking in 2022, but until now she didn't believe she had reached her full potential.

“Emotionally, I wanted it so bad,” Badosa said. "I'll never feel free until I win. I always do. It's my personality. It's my character."

In Thursday's semifinals, she will face her close friend and two-time defending Melbourne champion Aryna Sabalenka, as well as 2021 French Open runner-up Anastasia No. 27 Anastasia Pavlyuchenkova.

The Associated Press contributed to this report.