Alexander Zverev was stretched to the limit by a dogged Cameron Norrie before making it to the Australian Open quarter-finals after a grueling five-set battle on Monday.
The German sixth seed triumphed 7-5, 3-6, 6-3, 4-6, 7-6 (10/3) in a match that lasted more than four hours.
"At the end of the day it's a Grand Slam and everyone is playing at their best here," said Zverev. "Cam has definitely been playing amazing tennis and I'm just happy to get through."
Both players were solid on serve in the first set until Zverev won a 16-shot rally to earn two break points in the 11th game, making the vital breakthrough when Norrie netted.
The German, who had won all four of their previous Tour-level matches, broke first in the second set to ramp up the pressure on his 19th-seeded opponent but Norrie then went on a four-game winning spree to level the match.
A single break was enough to give Zverev the third set and the roles were reversed in the fourth set as Norrie hit back.
The scenarios quickly changed for the British number one, who dumped a forehand into the net to lose his serve in the opening game of the deciding set.
But he was back on level terms within minutes, breaking for the fourth time in the match. A wild forehand from Norrie in the seventh game handed Zverev two more break points but he failed to close the match. The deciding set went to a tie-break, which turned into a one-sided affair. Zverev raced into an 8-2 lead and he secured the match.
Meanwhile, Carlos Alcaraz reached the Australian Open quarter-finals for the first time, setting up a showdown against Olympic champion Zverev.
The 20-year-old Wimbledon champion missed the season-opening major in 2023 because of injury but is more than making up for lost time. The No 2 seed beat Miomir Kecmanovic 6-4, 6-4, 6-0 in less than two hours to open the night session on Rod Laver Arena.
He has dropped just one set en route to the last eight.
Also, two-time runner-up Daniil Medvedev overcame stubborn resistance from Portugal's Nuno Borges to book a place in the quarter-finals with a 6-3, 7-6, 5-7, 6-1 win. He will meet Polish ninth seed Hubert Hurkacz next.
World number three Medvedev, whose only Grand Slam title was at the 2021 US Open, was a Melbourne finalist in 2021 and 2022, losing to Novak Djokovic and Rafael Nadal.
But he said he had improved since.
"I know what I'm worth. I know how good I can play," he said. "I proved it at the US Open, especially for myself, playing some tough opponents, in my opinion, like gamestyle-wise. I managed to beat them.
"I'm ready. Hopefully I can show it on the tennis court. We can talk forever who is ready, who is favourite. You need to win."
In the women's section, seeded players continued to topple as Dayana Yastremska and Linda Noskova advanced to the quarter-finals.
Yastremska beat 18th seed Victoria Azarenka 7-6, 6-4, a two-time Australian Open champion, and No 23 seed Elina Svitolina had to retire after hurting her back when she was trailing Noskova 3-0.
Anna Kalinskaya beat No 26 seed Jasmine Paolini 6-4, 6-2 in a later match.
