MELBOURNE, Australia — World No. 6 Stefanos Tsitsipas joined an illustrious club in Wednesday’s Australian Open quarterfinal. The Greek joined Roger Federer and Fabio Fognini as the only players to ever come from two sets down to defeat 20-time Grand Slam champion Rafael Nadal.

Tsitsipas looked lost through most of the first three sets of his quarterfinal against Nadal, but somehow managed to bank the third set tiebreaker.

From that point, his confidence rose, as did his skill level, and after 4 hours, 5 minutes, Tsitsipas completed one of the most difficult tasks in tennis, in the process booking a place in the Australian Open semifinals for the second time in his career.

“I feel an extra connection with this court,” Tsitsipas said after his 3-6, 2-6, 7-6(4), 6-4, 7-5 win. “I’ve had moments that have elevated me and moments I will never forget.”

Here are the four moments that led to Tsitsipas’ sensational win.

The fitness factor

Tsitsipas did not have to take to the court for his fourth-round clash against Matteo Berrettini after the Italian withdrew an hour out from their contest, citing a nagging abdominal injury.

With a free pass through to the last eight, Tsitsipas spent Monday evening having a brief practice hit on one of Melbourne’s show courts, a far less strenuous excursion than if he’d come up against the world No. 9.

Plus, considering Tsitsipas is 12 years younger than Nadal, it’s clear he went into the quarterfinal the fresher of the two, though without immediate match fitness, something that showed early on. The No. 5 seed Tsitsipas didn’t get a look at a single break point opportunity through the opening three sets, the first two which Nadal won easily.

Third-set tiebreaker

It looked as if Nadal would be off the court, showered and back to his hotel room well before midnight, when he began the quarterfinal in similar fashion that got him to that point. After all, he had made it this far without dropping a set.

He and Tsitsipas held serve throughout the third to force a tiebreaker. After falling behind 2-1, Tsitsipas appeared to throw caution to the wind and attempt something he hadn’t done all match: overpower Nadal.

“I really didn’t care, honestly. I played with no care,” Tsitsipas said after the match. “It increased the level of tennis I put out there.”

He struck the ball with aggression and ferociousness, forcing Nadal deep in the court and into making some uncharacteristic mistakes.

“I think in the third he already started to play much better and I missed a couple of balls in the tiebreak that I shouldn’t,” Nadal said. “I could not miss if I wanted to win, and that’s it.”

From 2-1 down, Tsitsipas won five of the next six points before taking the tiebreaker 7-4. That was the catalyst for the comeback.

The service game factor

Nadal was dominant on serve throughout, not allowing his opponent even one break point opportunity in the first three sets.

But after taking the tiebreak, Tsitsipas tightened up his service games as well, not allowing Nadal a break point opportunity for the rest of the match.

Holding serve was key to Tsitsipas’ performance. From the start of the third set onward, he won an astonishing 75 of 94 points while on serve, dominating one of the greatest players to pick up a racket.

Tsitsipas finally forced a break in the ninth game of the fourth set, which ultimately sent it to a decider. In the fifth, Tsitsipas had just one break point chance — and he took it.

Final game

When Tsitsipas broke Nadal to take a 6-5 fifth-set lead, it appeared the Spaniard was on his way out of Melbourne Park.

But Tsitsipas left the door open for Nadal to counter when he opened the following service game with two unforced errors.

That’s when Tsitsipas delivered exactly what he needed: a 1-2 combination to force a Nadal error and back-to-back aces to bring up match point.

He couldn’t capitalize on his first match point, but at deuce, Tsitsipas painted the service box line with his first serve, giving Nadal no chance of returning the ball into play. On his second match point, Tsitsipas used a stunning down-the-line backhand to complete the comeback.

“I wasn’t really thinking about a lot of things,” Tsitsipas said. “I was … just there, playing — not thinking. I was mainly focused on each single serve, each single shot. At the third set I changed some things, changed my patterns, took some more time … these things kept adding up. I brainstormed.”