The stakes could not be higher as Novak Djokovic and Carlos Alcaraz square off in an Australian Open quarter-final clash of the tennis titans on Tuesday night.

So much history is on the line as 21-year-old Alcaraz, bidding to become the youngest man to complete a career grand slam, stands in the way of an unprecedented 25th major singles crown for Djokovic.

Sixteen years may separate the two, but already Djokovic and Alcaraz have forged a compelling rivalry highlighted by two Wimbledon finals, a Paris Olympic gold medal showdown, and semi-finals at Roland Garros and the 2023 ATP season-ending championship.

Never before, though, have Djokovic and Alcaraz met in a quarter-final.

Players of their grand stature are only supposed to meet at the pointy end of tournaments, like when Alcaraz denied the super Serb in the past two Wimbledon title deciders, before the 24-times major champ completed an elusive golden slam in Paris last August.

"Well, this is not the right player to play in a quarter-final," Alcaraz mused.

"But facing Novak, for me it's not going to change anything if I'm playing him in quarter-final or semi-final.

"I'm going to approach the match the same as I did in the previous matches against him, and let's see."

That approach from the Spanish sensation is once again to block out Djokovic's aura of invincibility, especially at Melbourne Park, where the 37-year-old has reigned an incredible 10 times.

"I'm trying not to think about that," Alcaraz said.

"If I think about everything he has done in tennis, I couldn't play.

"I mean, 24 grand slams, the most weeks at No.1, everything. He almost broke every record in tennis.

"I'm trying not to think about that when I'm in the match. I'm just trying that I'm able to beat him.

"I know my weapons. I know that I'm able to play good tennis against him, I'm able to beat him.

"That's all I'm thinking when I'm facing him."

Djokovic leads the 21-year-old 4-3 head-to-head, but is once again "expecting a big battle".

"As is the case in most of our matches where we faced each other," he said.

"Maybe just a couple (of) times it was quite one-sided. Wimbledon finals last year, he was the dominant force on the court.

"I had a really good match against him in the World Tour Finals in 2023.

"Other than that, we had some long battles, long exchanges kind of matches that I played against him. (They) remind me of my match-ups versus (Rafael) Nadal in terms of the intensity and the energy on the court.

"He's a very dynamic, explosive player. Incredibly talented. Charismatic player. Great to watch; not that great to play against.

"I look forward to it. I think when the draw was out, a lot of the people were looking forward to potential match-up in quarter-finals, Alcaraz versus me.

"So here we are."

Djokovic has been stranded on 24 slams, alongside Margaret Court, since winning the 2023 US Open final, then failing to win a major last season for the first time since 2010.

Alcaraz completed the rare French Open-Wimbledon double last year to go with his 2022 US Open title and 2023 victory at the All England Club.

The winner of their latest blockbuster will face either German world No.2 Alexander Zverev or American 12th seed Tommy Paul in the semi-finals on Friday.

7-NOVAK DJOKOVIC (SRB) leads 3-CARLOS ALCARAZ (ESP) 4-3 (2-1 at grand slams)

2024 Paris Olympics, clay, F, Djokovic 7-6 (7-3) 7-6 (7-2)

2024 Wimbledon, grass, F, Alcaraz 6-2 6-2 7-6 (7-4)

2023 ATP Finals, indoor hard, SF, Djokovic 6-3 6-2

2023 Cincinnati Masters, hard, F, Djokovic 5-7 7-6 (9-7) 7-6 (7-4)

2023 Wimbledon, grass, F, Alcraraz 1-6 7-6 (8-6) 6-1 3-6 6-4

2023 French Open, clay, SF, Djokovic 6-3 5-7 6-1 6-1

2022 Madrid Masters, clay, SF, Alcaraz 6-7 (5-7) 7-5 7-6 (7-5)