MELBOURNE, Australia -- Gael Monfils is one of the most athletic and fit players in men's tennis, but in the closing moments of his second-round match against Novak Djokovic, the Frenchman was staggering around between points at Rod Laver Arena like a punch-drunk boxer.

Juan Martin del Potro has been bravely recovering from a wrist injury that has led to multiple surgeries the past two years, but that had nothing to do with the No. 12 seed getting treatment from a trainer while stretched out on the court during his final few games against Karen Khachanov.

Gael Monfils appeared delirious at times during his second-round loss against Novak Djokovic. AP Photo/Vincent Thian

Djokovic and del Potro both won in four sets, but the bigger story was the extreme heat, which tournament officials said was recorded at 104 degrees at 5:30 p.m. at Rod Laver Arena.

About that 5:30 reading: That came when shade was beginning to cover the court area. You can bet the on-court reading earlier in the day -- when play took place under direct sunlight -- was even higher. (Officials said they had no earlier numbers to report.)

"I got super dizzy," said Monfils, who told the chair official to forget the new rule that requires players to serve within 25 seconds between points. "I think I had a small heat stroke for 40 minutes."

That's right, Monfils claims he had a heat stroke. And Djokovic says the conditions were on the precipice of being dangerous to the players' health.

"It was right at the limit," Djokovic said. "Our sport has become an industry, like most of the other global sports. ... At the same time, what is most important for us is our health and what happens after our career, after you're 30, 35. It's a very complex subject to talk about."

Extreme heat -- and the decision to play or not to play -- is, indeed, complex and difficult to understand. The tournament's Extreme Heat Policy allows stoppage of play (or roof closures) when a temperature of 40 degrees Celsius (102 degrees Fahrenheit) coincides with a WetBulb Globe temperature index reading surpassing 32.5.

Say what?

Without any background in atmospheric science or climatology, I don't have a clue about the relationship between temperature and WetBulb Globes. But I do believe, if you break it down to layman's terms, an official can stop play when it gets really hot.

On Thursday, it was really hot.

"Maybe too hot," Monfils said.

This fan's reaction says all you need to know about the heat Thursday at the Australian Open. PAUL CROCK/AFP/Getty Images

Rafael Nadal predicted the storyline for Thursday when asked a day earlier about the predicted heat wave.

"I think it is a health issue," Nadal said. "I like to, sometimes, play in heat. When it is too much, it becomes dangerous for our health. If the courts have roofs, why not put the roof on when the conditions are extreme?"

A closed roof could have possibly made for better, cleaner play in the nearly three-hour match between Djokovic and Monfils that the Serb won 4-6, 6-3, 6-1, 6-3. (Monfils had 65 unforced errors to Djokovic's 40.)

And a closed roof could have made for a better experience for fans. Each arena had a predictable look from the start of the morning matches through the rest of the afternoon. Sections of seats exposed to direct sunlight were nearly entirely empty, save for a few brave fans.

Jessica Marintelli was one of those brave fans. When ticket holders abandoned their primo midcourt, lower-level seats at Rod Laver Arena, the Western Australian left her upper-level seat and claimed their territory.

The huge Djokovic fan wound up having an entire row to herself.

But that came at a price.

"These seats are hot; they are burning, and if you touch them it feels like your clothes are on fire," said Marintelli, whose discolored nose was in clear need of some ointment. "It was very, very hot. I put sunscreen on about six times and kept covering myself with cold water."

So why sit in the heat near the center of the court, when she would have easily grabbed a shady seat in one of the corners?

"I'm from Perth, so I'm used to this," she said. "And it's Novak Djokovic. I want to be able to see him from the best seat possible."

Del Potro was so impacted by the heat that it took him nearly three hours at the end of his match to meet with the media."

"It was really difficult to play," del Potro said. "The temperature was too high for playing tennis. Also, if you saw the crowds, nobody was there watching under the sun."

Djokovic was so impacted by the heat that he urged tournament officials to throw their EHP equations out the window and rely common sense.

"There are certain days where you just have to, as a tournament supervisor, recognize that you need to give players a few extra hours until [temperatures] come down," Djokovic said. "I understand there is a factor of tickets. But there is a limit of being fit to play and being, I think, in danger to your health."

It was tough to witness. On my walk to Rod Laver Arena, an older woman collapsed near the tournament's media center. She appeared to be overcome by the heat.

There was nothing the tournament officials could have done to protect her.

But there is something they can do to protect the players. On Thursday, despite the numerous complaints from the players, the officials did not release any kind of statement, though the Australian Open Twitter handle had these words:

The health of our players is of paramount concern, but we need to be consistent with the outside courts so some don't get an unfair advantage. The referee will initiate the Extreme Heat Policy once the ambient temperature exceeds 40C & the Wet Bulb index (WBGT) exceeds 32.5C. — #AusOpen (@AustralianOpen) January 18, 2018

The Extreme Heat Policy comes into effect once the ambient temperature exceeds 40C & the Wet Bulb index (WBGT) exceeds 32.5C. The health of our players is of paramount concern to us, and we are constantly monitoring conditions. Let's hope it cools down! — #AusOpen (@AustralianOpen) January 18, 2018

[6:42 AM]

On Friday, it's expected to be hotter -- possibly as high as 105 degrees -- and tournament officials will be facing tough decisions.

Monfils, who called Thursday's conditions the toughest he's ever played in, had only these words for his peers scheduled to play Friday.

"Honestly, good luck for the guys," he said. "Good luck to them."