Coco survives Kostyuk test to reach Australian Open semis

US Open champion Coco Gauff came through a huge test at the hands of Ukrainian world number 37 Marta Kostyuk 7-6(6) 6-7(3) 6-2 to reach the semifinals of the Australian Open for the first time on Tuesday.

The fourth-seeded American will rarely play as badly and still progress but prevailed after more than three hours on a blistering hot Rod Laver Arena to fulfil her coach Brad Gilbert's famous maxim by "Winning Ugly".

"I'm really proud of the fight I showed today, Marta's a tough opponent, every time we play it's a tough match," she said.

"Yeah, I really fought and left it all out on the court today." Gauff, playing her final Grand Slam as a teenager, had swept into the last eight on a nine-match winning streak as she looked to back up her first major success in New York last year.

Kostyuk got right in the American's face from the off, however, and stormed to a 5-1 lead, serving twice for the opening set as well holding a set point on Gauff's serve.

The 19-year-old American knew she was up against it and, problem-solving on her feet, battled her way back into the contest by rattling off five successive games to serve for the set herself.

"I was just trying to get one more game in the first set and make it more competitive, then one game turned into another and I was able to win that set," Gauff added.

Kostyuk had been looking increasingly frequently at her coach as her confidence waned but she earned three break points off Gauff's forehand and forced the tiebreak when the American double-faulted.

The Ukrainian was revived by treatment on blisters on her feet before the tiebreak but blew her second set point, allowing Gauff to come racing into the net to go a set up.

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