Open walkover moves Alcaraz closer to career grand slam

"Obviously it's not the way I wanted to get through," Alcaraz told reporters after spending just an hour and 35 minutes on Rod Laver Arena.

Draper was backing up after three five-set marathons in a row, including victories over locals Thanasi Kokkinakis and Aleksandar Vukic in hostile territory.

The 23-year-old Brit said the gruelling matches had worn on an existing hip tendonitis injury that forced him to withdraw from the United Cup.

Carlos Alcaraz in action against Jack Draper. (James Ross/AAP PHOTOS)

"Obviously in the pre-season, it (got) into my back and I couldn't walk and it was really difficult," Draper said.

"We were managing it. Maybe it's a little bit of a ticking time bomb."

With the temperature hovering above 33C at Melbourne Park, Alcarez faltered when serving for the first set at 5-3 and remonstrated at the chair umpire at the change of ends over an ill-timed shot clock violation.

But the Spaniard steadied himself and sealed the first set with a trademark running forehand winner down the line.

Draper, who prevailed in the pair's most recent encounter on home soil at Queen's Club last year, retreated to the dressing rooms between sets for medical treatment but was still restricted on his return.

Jack Draper leaves the court after his injury retirement. (James Ross/AAP PHOTOS)

Alcaraz is seeking to become the youngest man to complete a career grand slam after earning titles at Wimbledon in 2023 and 2024, the US Open in 2022 and the French Open in 2024.

His first attempt at the feat at Flushing Meadows last year went up in flames with a shock second-round loss to Dutchman Botic van de Zandschulp

"I'm one step closer," Alcaraz said when asked if the accomplishment was playing on his mind.

"But what I've learned in the previous grand slam that I've played is going day by day in a grand slam."

Alcaraz's bogey slam has been the Australian Open, where he reached the quarter-finals for the first time last year before being stopped in his tracks by Alexander Zverev.

Sunday's walkover sets up a likely quarter-final blockbuster with 10-time Australian Open champion Novak Djokovic, who faces Czech 24th seed Jiri Lehecka on Sunday evening.

Earlier, American Tommy Paul became the first man into the quarter-finals by ending the dream run of Spain's Alejandro Davidovich Fokina.

Tommy Paul blasted his way into the last eight. (Lukas Coch/AAP PHOTOS)

The 12th seeded Paul showed no mercy against the battle-weary Davidovich Fokina, winning 6-1 6-1 6-1 in an hour and 27 minutes on Margaret Court Arena.

It is the second time 27-year-old Paul has reached the last eight in Melbourne following a semi-final appearance in 2023.

Davidovich Fokina appeared to be hampered by a groin injury after battling back from two sets down to defeat former world No.6 Felix Auger Aliassime and Czech rising star Jakub Mensik in the previous two rounds.

Davidovich Fokina's heroic run came to an end against Tommy Paul. (Lukas Coch/AAP PHOTOS)

"What he did is unreal in the past couple of matches," said Paul, who had beaten the 25-year-old in all four of their previous encounters.

In the evening session, world No.2 Zverev booked a last-eight date with Paul, recovering from dropping his first set of the tournament to defeat French 14th seed Ugo Humbert 6-1 2-6 6-3 6-2.

The 27-year-old German is on the wrong side of a 0-2 record against Paul but hasn't played him since 2022.