Defending champion Roger Federer was dramatically knocked out of the Australian Open by 20-year-old Stefanos Tsitsipas on Sunday night in a match John McEnroe described as “the changing of the guard”.

Greece’s Tsitsipas won a thrilling tussle 6-7 (11-13) 7-6 (7-3) 7-5 7-6 (7-5) in three hours and 45 minutes at the end of a day that also saw Ashleigh Barty reach her first Grand Slam quarterfinals by defeating Maria Sharapova.

Tsitsipas’ win might have been a surprise, but to call it a shock would be to do him a disservice. 

After all, he won the Next Gen ATP Finals in 2018, beating Alex de Minaur in the decider, has a world ranking of 15 and entered the Melbourne Park grand slam as the 14th seed.

Tsitsipas’ talent is obvious but it was his ability to outlast Federer when it really counted that made the biggest impression.

Men’s tennis has been crying out for a new generation for some time.

Federer is 37 and Andy Murray is likely to retire soon, while Rafael Nadal’s body does not allow him to play in as many tournaments as he would like. 

Novak Djokovic has had his struggles, too, and although the six-time Australian Open champion looks in ominous touch at the moment, he is also on the wrong side of 30.

All of that means a door that has remained closed for years is now ajar, with the likes of Tsitsipas, De Minaur and 21-year-old Frances Tiafoe trying to pry it open further. 

Tsitsipas, who said he had been analysing Federer since he was just six years old, was elated with victory.

Stefanos Tsitsipas celebrates his victory against Roger Federer during their men’s singles match. Photo: Getty

“It was a very emotional moment [when victory was sealed],” Tsitsipas told reporters.

“It was something – a beginning of something really big. I felt joy. I felt happiness. That moment is definitely something that I will never, ever, ever forget.

“This win is a good milestone – let’s say, good first step, as I said, to something bigger.”

Tsitsipas will face Spaniard Roberto Bautista Agut in the last eight as Federer’s dreams of a third successive grand slam title in Melbourne were dashed.

The Swiss maestro, who could not convert any of his 12 break points in the clash, was asked about McEnroe’s post-match assertion but was not as convinced.

“He’s in front of the mic a lot – he’s always going to say stuff,” Federer said.

“I love John. I’ve heard that story [about a new generation] the last 10 years. From that standpoint, nothing new there.”

Federer, who said he had “massive regrets” after the match, did admit that Tsitsipas deserved a lot of credit for his win, insisting he “lost to a better player who was playing very well tonight”.

“[He] hung in there, gave himself chances at some point, stayed calm,” he added.

“It’s not always easy, especially for younger guys. Credit to him for taking care of that.”

Barty downs Sharapova in comeback win

Earlier on Sunday, Barty became the first Australian woman to reach the quarter-finals at Melbourne Park since Jelena Dokic achieved the feat in 2009.

Barty came from behind to defeat Sharapova 4-6 6-1 6-4 in a see-sawing clash on centre court.

Maria Sharapova (L) congratulates Ashleigh Barty (L) on winning their fourth round match of the Australian Open. Photo: Getty

The former World No.1 took the opener but struggled on serve after that, producing 10 double-faults that regularly gave Barty chances.

The home favourite raced through the second set and then took a 4-0 lead in the decider but Sharapova made it a contest, reducing the margin to 4-3 in a tense affair.

Barty eventually held firm, though, setting up a last-eight clash with Petra Kvitova, the Czech player who beat her in the final of the Sydney International earlier this month.

“One of the ultimate goals for ’19 was to try and really get my teeth sunk into slams and get deep into the second week,” she said afterwards.

A quarter-final appearance is Barty’s best ever grand slam result.

Around the courts

American Danielle Collins produced a big shock when she thrashed second seed Angelique Kerber 6-0 6-2 in just 56 minutes. 

Kvitova won in similarly comfortable fashion against Amanda Anisimova.

In the men’s singles, Nadal proved far too good for Tomas Berdych, winning 6-0 6-1 7-6 (7-4), while the former’s compatriot, Bautista Agut, won another five-setter.

Bautista Agut downed 2018 finalist Marin Cilic 6-7 (6-8) 6-3 6-2 4-6 6-4.

Tiafoe also won through to the quarter-finals, surprising Grigor Dimitrov 7-5 7-6 (8-6) 6-7 (1-7) 7-5 on his 21st birthday.

And in the final match of Sunday’s schedule, that finished at 1.54am on Monday (AEDT), unseeded Russian Anastasia Pavlyuchenkova surprised fifth seed Sloane Stephens 6-7 (3-7) 6-3 6-3.