John McEnroe has declared “the official changing of the guard” in men’s tennis after Jannik Sinner and Carlos Alcaraz claimed all four Grand Slams this year.

And the Italian world No.1 welcomed the “new generation” taking over the sport with “new rivalries” after decades of domination by the Big Three.

The Australian Open champion, 23, became the youngest man to ever complete the calendar hardcourt double by beating Taylor Fritz in the US Open final.

And with Alcaraz, 21, winning the French Open and Wimbledon, it is the first time since 1993 that all four Majors in the same year have been won by players 23 or younger.

It is also the first time since 2002 that none of Novak Djokovic, Rafa Nadal and Roger Federer have won a Grand Slam. And McEnroe told ESPN: “It is the official changing of the guard. When was the last time none of the Big Three won a Grand Slam?”

But the American legend, 65, also claimed that there will now be a greater variety of male champions – with US Open semi-finalist Jack Draper among the contenders.

“I do think it will open the minds of other players to think they have got a shot at it as well,” said the seven-time Grand Slam champion. “These guys can’t possibly – can they? – dominate like these last three guys have. Alex Zverev is currently No.2 in the world after this tournament. Those guys who have been bypassed, you would think it would increase the hunger to finally get over the hump and win one.”

Olympic champion Novak Djokovic, who turns 38 in May, will still be a contender next year and can win his record-breaking 25th Grand Slam singles title in Australia in January.

But for now, there is a new Big Two. Alcaraz posted on X: “Congratulations @janniksin. You deserve it! Enjoy the moment!”

And asked about his 2024 clean sweep with the Spaniard, the Italian said: “It is a bit different, for sure. It’s something new. It’s nice for the sport to see some new champions. Nice to see new rivalries. I feel like the new generation we push each other, trying to improve. I feel it’s good for the sport to have some new champions.”

Starting in Melbourne in January, Sinner has now won all six finals this season. And the Italian warned he is only going to get better. “Today we saw that not everything was perfect,” he said “The work never stops. We always try to evolve in my game.”

And he is only the third man in the Open Era – after Jimmy Connors in 1974 and Guillermo Vilas in 1977 – to win his first two Grand Slam titles in the same year.

Yet Sinner will also be remembered for winning after failing the same number of drug tests in March. He was cleared after an independent tribunal accepted his defence that he had been accidentally contaminated by his physio during massages.

Americans don’t do irony and Andre Agassi, who escaped a ban after testing positive to Crystal meth in 1997, presented the trophy.

Emotional Sinner, who was embraced by girlfriend Anna Kalinskay and his superfan Seal after the win, thanked his team “family” for their support.

His coach Darren Cahill told ESPN: “Today has been amazing considering what he has been through. It has been a journey the last three weeks for sure. It has been like carrying 20kgs on his shoulders for the past four months. And then 40kgs on his shoulder for the last three weeks.”

But the noise has not stopped with a Slam. When Piers Morgan posted about Sinner winning after his two failed drug tests, Sinner’s chief troll Nick Kyrgios responded: “For the first time in history! We are witnessing greatness.”

Asked how the tennis world will react to his second Grand Slam title, the Italian said: “I don’t know. You have to ask all the other players. The general reaction of the players was quite positive, even when things came out. Then there have been, of course, some different voices, but this is in everything. I just can talk from my side and from my team’s perspective, and we are all very proud of this achievement.”