Melbourne, Australia — Elina Svitolina ended 15-year-old Marta Kostyuk's run at the Australian Open, met her at the net for a warm embrace and offered some words of encouragement.

With the temperature hitting 40 degrees Celsius (104 Fahrenheit) for the second straight day, fourth-seeded Svitolina reached the fourth round at the season-opening major for the first time with the 6-2, 6-2 win on Rod Laver Arena.

"She's a great fighter," Svitolina, one of five women in contention for the No. 1 ranking, said of her fellow Ukrainian. "We're going to hear a lot more about her."

Players were bothered and spectators clamored for shade and mist-spraying fans in searing heat at Melbourne Park, which had organizers on the verge of enforcing the tournament's extreme heat policy before temperatures dropped quickly after peaking around 2 p.m. local time.

Play can be suspended at the Australian Open if the temperature 40 Celsius (104F) and a combination of factors - including temperature, humidity and breeze - reaches an unbearable limit.

Alize Cornet, who needed a medical timeout and a doctor to take her blood pressure as she struggled with heat stress in her 7-5, 6-4 second-round loss to Elise Mertens, was among those suggesting the extreme heat policy needs reviewing.

"I started to feel dizzy. ... I was feeling super, super hot. I kind of felt that I could faint at any moment," she said, adding that while precautions were taken by tournament officials, "playing in this condition is of course very dangerous for the health of the player.

"The limit of not playing the match is really high. ... I think this limit should be a little bit lower."

No. 3-seeded Grigor Dimitrov beat No. 30 Andrey Rublev 6-3, 4-6, 6-4, 6-4 in just over three hours in an afternoon match on Rod Laver Arena and said, "the heat didn't scare me at all today - that's a good sign."

His fourth-round opponent was to be decided later in the match between local hope Nick Kyrgios and 2008 finalist Jo-Wilfried Tsonga.

Kyle Edmund was the first man into the fourth round, overcoming Nikoloz Basilashvili 7-6 (0), 3-6, 4-6, 6-0, 7-5 in 3 ½ hours on open court in the peak of the heat. No. 10 Pablo Carreno Busta had a 7-6 (4), 4-6, 7-5, 7-5 win over No. 23 Gilles Muller.

Kostyuk entered the tournament ranked No. 521 - a number that will likely be halved next month - and had wins over 25th-seeded Peng Shuai and Olivia Rogowska to become the youngest player to win main-draw matches at the Australian Open since Martina Hingis in 1996.

The step-up to facing a top 10 player was too much for Kostyuk on Friday.

She had nine double faults, including on match point, and only put 37 percent of her first serves into play.

Svitolina, the only seeded player still in contention in her quarter, had five aces, only 11 unforced errors and didn't serve a double fault in the 59-minute match.

Kostyuk sobbed into a towel in the tunnel soon after leaving the court, but could joke about the defeat when asked later what she could take out of the experience.

"Well, a lot," she said. "How much you have to pay Svitolina to have one-hour lesson? I got it for free."

Kostyuk received entry into qualifying because of her junior girls' victory last year at the Australian Open. She won all three qualifying matches, then her first two in the main draw.

Svitolina will next play Denisa Allertova, who beat Magda Linette 6-1, 6-4. No. 19 Magdalena Rybarikova had a 7-5, 3-6, 6-1 win over Kateryna Bondarenko.

In the opening match on Rod Laver Arena on Day 5, Petra Martic celebrated her 27th birthday with a 6-3, 3-6, 7-5 over Thai qualifier Luksika Kumkhum.

"That was really ugly," Martic said of the heat. "We were lucky to play on Rod Laver because we had some shade behind, so you could hide for a few seconds in between the points.

"Other than that, you need to be mentally tough and ready to just suffer out there."