MELBOURNE, Australia >> Coco Gauff’s retooled forehand and serve abandoned her in the worst way and at the worst time at the Australian Open. The unforced errors just kept accumulating Tuesday, and so did the double-faults and break points, often followed by a palm placed over her eyes or a slap to a thigh.

Add it all up, and Gauff’s trip to Melbourne Park — and her 13-match winning streak that dated to late last season — ended in the quarterfinals. Never able to take control on a hot afternoon in Rod Laver Arena, the 2023 U.S. Open champion was eliminated by No. 11 Paula Badosa of Spain 7-5, 6-4.

Using tweaks to some key strokes, and a change to her coaching team after a disappointing end to her title defense in New York in September, the 20-year-old Gauff arrived in Australia with hopes of earning a second Grand Slam title.

“I feel like (at the) U.S. Open, I was playing with no solution, so that was more the frustrating part. Today, I feel like I’m playing with solutions; I know what I need to work on. U.S. Open, I needed to work on my serve. Not saying that my serve is where I want it to be, but I worked on it; obviously, a big improvement. So I want to continue working on that, continue working on playing aggressive,” Gauff said.

“So I feel like I’m on the road to the right way, right path,” she said. “Even though I lost today, I feel like I’m in an upward trajectory.”

Badosa now heads to her first Grand Slam semifinal at age 27 — and less than a year after she was contemplating retirement because of a stress fracture in her back that took what felt like forever to heal and did not initially respond to cortisone injections.

In Thursday’s semifinals, she will go up against her close friend, No. 1 Aryna Sabalenka, the two-time defending champion in Melbourne. Sabalenka stretched her winning streak in the tournament to 19 matches by getting past No. 27 Anastasia Pavlyuchenkova 6-2, 2-6, 6-3.

Novak Djokovic reached his 50th Grand Slam semifinal as he pursues a record 25th trophy at a major, getting past Carlos Alcaraz 4-6, 6-4, 6-3, 6-4 across more than 3 1/2 hours in a match that ended at nearly 1 a.m.

Djokovic took a medical timeout late in the first set to get his left leg taped but later said he eventually felt better thanks to pills he was given by the tournament doctor.

Djokovic will now face No. 2 Alexander Zverev, a two-time finalist at other majors, on Friday. Zverev got to the final four in Melbourne for the third time since 2020 by beating No. 12 Tommy Paul 7-6 (1), 7-6 (0), 2-6, 6-1.