Change of guard? Not yet

At the start of every year the talk at the Australian Open is of the "new kids on the block", the "NextGen", the "young guns".

And every 12 months as the first Grand Slam heralds a fresh season they come... and they go.

Roger Federer, Rafael Nadal and Novak Djokovic's stranglehold on the Norman Brookes Challenge Cup has been interrupted just twice since the Swiss master first lifted it in Melbourne in 2004.

Marat Safin (2005) and Stan Wawrinka (2014) managed to interlope into the trio's private sanctum -- and they were 25 and 28 years old respectively at the time, hardly fresh-faced youths.

But this year seems different.

The simple truth is the big three cannot halt Old Father Time and one day soon will retire from slugging it out around the world. We may have already seen the last of stricken Andy Murray.

So when young Stefanos Tsitsipas sent third seed Federer packing on Sunday at the tender age of 20, after giant-killer Frances Tiafoe also reached the last eight, it seemed the tennis world may at last be shifting on its axis.

Trouble is, to do it at least one of them will need to find a way to stop the raging bull that is Nadal if they are to win a maiden Grand Slam with the American up first against the Spanish giant in a quarterfinal on Tuesday.

Tiafoe -- who at the age of 20 had already caused a shock in stunning fifth seed Kevin Anderson in the second round -- registered another notable scalp on his 21st birthday.

This time it was against Grigor Dimitrov, now 27, who was nicknamed "Baby Fed" in his early twenties and himself tipped as the next big thing.

But "Daddy Fed", Roger himself, is tired of the constant chatter "about a changing of the old guard".

"I've heard that story the last 10 years. From that standpoint, nothing new there," Federer said.

And the great man signalled that, at the age of 37, he was not going away by announcing he would play on clay at the French Open this year for the first time since 2015.

Federer did concede that his young conqueror, the exciting Greek who appears to have all the gifts, was beginning to establish himself.

"About Stefanos, I think he's definitely done a really nice job now the last year and a half," said the 20-time Grand Slam champion.

"I mean before that, too, obviously. But beating Novak in Toronto, the likes of Anderson and (Alexander) Zverev, now me here. That's what you need to do to get to the next level. He's doing that."

The popular Tiafoe plays with a smile on his face, a roar in his voice and has plenty of admirers too.

"It's so nice to see somebody new, somebody fresh," said Dimitrov.

"I mean, everybody in the locker room likes him, everybody is laughing. He's going to be amazing. He can only get better from now on, for sure."

But the Bulgarian, who has not yet fulfilled his own huge potential, sounded a cautionary note.

"I know how it is to break grounds on those first tournaments, especially a Slam," he said.

"He really needs to just stay calm and make sure he follows the right path.

"I mean, one thing is to do well at one tournament, but another thing to do it progressively."