In pics: Day 7 highlights of Australian Open

Roger Federer was knocked out of the tournament, while Ashleigh Barty became the first Australian woman in a decade to reach the quarter-finals. 

Two-time defending champion Roger Federer was knocked out of the Australian Open after he was beaten in four sets 6-7 7-6 7-5 7-6 by Stefanos Tsitsipas.

The Swiss had 12 breaks points that slipped through his grasp as his hopes of a 21st Grand Slam title were ended on Sunday. 

Ashleigh Barty became the first Australian woman in a decade to reach the quarter-finals at Melbourne Park when she rallied from a set down to beat former champion Maria Sharapova 4-6 6-1 6-4 on Rod Laver Arena.

With the challenge from Australian men's singles players having fizzled out in the early hours of Sunday morning, Barty is the last player standing who could quench the nation's thirst for a first home champion since Chris O'Neil in 1978.

Five-time major winner Sharapova claimed her biggest scalp since completing a drugs ban in 2017 when she rolled defending champion Caroline Wozniacki in round three and looked on track to carry the momentum forward.

Despite offering some late resistance, and some unbelievable tennis, there was no way back for the 2008 champion.

Rafael Nadal routed Tomas Berdych 6-0 6-1 7-6(4) in a centre court masterclass to charge into the quarter-finals.

The 2009 champion was relentless at Rod Laver Arena, claiming the first two sets in an astonishing 51 minutes and firing 32 winners past the hapless Czech to reach the last eight at Melbourne Park for the 11th time.

Former world number four rallied to grab a set point off Nadal in the final stanza but an untimely malfunction of the serve clock rattled him during the ensuing tiebreak and he bowed out slapping a backhand into the net.

Nadal ploughed on to 3-0 in the second set before Berdych finally held, raising ironic cheers in the terraces.

The memory of Berdych's famous quarter-final win over the Spaniard at the 2015 tournament can never have seemed foggier for the 33-year-old, whose 2018 season was cut in half by a back injury.

Roberto Bautista Agut held firm in a tense five-set duel to knock sixth seed Marin Cilic out of the tournament and booked his maiden Grand Slam quarter-final on Sunday.

The 22nd-seeded Spaniard captured the decisive break in the ninth game of the final set before serving out strongly to claim a 6-7(6) 6-3 6-2 4-6 6-4 win at Margaret Court Arena.

The 30-year-old will face the winner of the match between Roger Federer and Stefanos Tsitsipas for a place in the semi-finals.

Unseeded American Frances Tiafoe gifted himself the perfect 21st birthday present by stunning Bulgaria's Grigor Dimitrov 7-5 7-6(6) 6-7(1) 7-5 in the match.

The last American man standing at Melbourne Park, Tiafoe was treated to an enthusiastic rendition of Happy Birthday by the Melbourne Arena crowd after sealing a spot in his first Grand Slam quarter-final.

"I told my parents 10 years ago that I was gonna do this, I was gonna change their lives and my life," an emotional Tiafoe said courtside.

"Now I'm in the quarters of a slam at 21. I can't believe it, man."

Former Melbourne semi-finalist Grigor Dimitrov had three sets points to draw level but Tiafoe refused to wilt under the pressure and reeled off five straight points to move two sets ahead.

Dimitrov, who has slipped just outside the top 20 in the world after early exits in his last three Grand Slams appearances, would not go out without a fight, though, and took the third set in another tiebreak, but was finally defeated.

American Danielle Collins took less than an hour to thrash 2016 champion Angelique Kerber 6-0 6-2 and power her way into the quarter-finals.

The unheralded 25-year-old had not won a match in her previous Grand Slam appearances but after smashing 29 winners against triple Grand Slam champion Kerber she has now made it to the last eight in her first main draw showing at Melbourne Park.

"I may not have won a Grand Slam match before this (but) I got to tell you I think it's going to keep happening," Collins said.

Wimbledon champion Kerber mumbled to herself constantly, unable to show any fight she threw down her racquet in frustration that brought a warning from the umpire.

After an early trade of breaks in the second set, Kerber's serve was broken by Collins as she smashed a backhand and took a 4-2 lead. The German once again lost and Collins sealed victory on her first match point in 56 minutes.