Alcaraz, 19, is leading the charge after becoming the youngest world number one since the creation of the ATP rankings in 1973 by winning his first Grand Slam tournament at the US Open last September.

He then became the youngest player in history to finish the year at the top of the rankings, and the first outside of Djokovic, Nadal, Federer and Andy Murray to do so since Andy Roddick in 2003.

Danish teenager Holger Rune, who shocked Djokovic to clinch his first Masters title in Paris in November, is another on the charge, along with the likes of world number three Stefanos Tsitsipas.

Nadal praised the ‘next-gen’ as “super-good” but said he wasn’t sure they could dominate in the way he, Djokovic and Federer have.

“Carlos has one Grand Slam, the others have zero yet. If we start talking about achieving 22 Grand Slams, 21, 20, I mean, it’s a big deal,” he said.

“That can happen, yes. Why not? But at the same time it never happened in the past. Will not be easy that happens two generations in a row.

“That’s just putting the logical perspective on the room,” he added.

“They are super good, they’re going to have amazing careers, they’re going to win Slams, they’re going to win a lot of tournaments, yes.

“But I’m almost sure not two players of this generation are going to achieve 20, 21, and 22 Grand Slams.”

World number one Alcaraz is not at Melbourne Park after pulling out with an injury.

Nadal said it was easy for people to forget how hard it had been for himself and his two great rivals to achieve what they had.

“I mean, probably because there have been three players that achieved that much, we lose a little bit of perspective of how difficult all of this is,” he said.

“We are here playing tennis at the age of 36, and you need to have a very, very long career. Injuries are there, circumstances in life.

“Don’t talk about the level of tennis because that’s probably a thing you can have, but then there are a lot of different facts in life that can happen that makes this situation or these results difficult.”