Jannik Sinner left visibly shaking in disturbing scenes at Australian Open

Sinner also benefited from a 21-minute delay in the fourth set when his first service game broke the metal ring connecting the net to the hard court at Rod Laver Arena. During the delay, he had the luxury of taking another medical timeout to recuperate from heat exhaustion. 

After his testing win, Sinner revealed he was forced to skip practice before Monday's match due to dehydration issues.

"I was not feeling really well," he said, via The Guardian. "I think we saw that today, I was struggling physically. Came here as late as possible. I knew that it was going to be very, very difficult today – playing against a tough opponent, but also playing against myself a little bit."

A humbled Sinner admitted that he may have lost the match without the 21-minute delay or the outpouring of crowd support. 

"I was lucky today that [at] this point, 20 minutes off court, trying to get back physically, putting some cold water in my head, it was very helpful. It was big, big luck to me today," he added. 

Sinner gave the boisterous Melbourne crowd "90 percent" of the credit for his victory. At various points in the match, the fans egged Sinner on when he seemed on the verge of an upset loss.

The defending champion will face either 20-year-old American Alex Michelsen or World No. 8 Australian Alex de Minaur in the quarterfinal. 

Sinner has now won 18 consecutive hard-court major matches, dating back to his wins in last year's Australian Open and U.S. Open. At 23, he's become the youngest player since John McEnroe in 1981 to maintain such a grand slam streak on hard courts. With a 44-3 record as World No. 1, Sinner has surpassed the great Bjorn Borg with the best winning percentage as the top-ranked player since 1973.