Twelfth seed Ben Shelton dispatched the French veteran Gaël Monfils on Monday to move into the quarter-finals at the Australian Open for the second time in three years.
The 22-year-old American was leading two sets to one and had just taken the first game of the fourth set when his 38-year-old opponent retired due to exhaustion.
"In the third set, I felt I'd crossed a physical limit," said Monfils, who was the last of the 13 French players who had been competing in hte main draw at the championships. "I was burnt out."
Monfils entered his 19th Australian Open on the back of the crown in Auckland. The 13th trophy of a career spanning two decades brought him the accolade of becoming, at 38-years and four months, the oldest man to brandish a senior level title since tennis was opened to professional players in 1968.
He used that momentum to edge past his big-serving compatriot Giovanni Mpetshi Perricard in five sets in the opening round in Melbourne. More of his savviness was on show during the straight-sets dismissal of the unseeded German Daniel Altmaier in the second round.
Monfils then caused one of the shocks of the 2025 tournament when he took out the fourth seed Taylor Fritz in the third round.
"To push me the way he did today and entertain everyone is so impressive," said Shelton of Monfils' exploits. "He had played a lot of long matches and I wanted to make it as physical as possible.
Tricky
"But it was really tricky today because he was serving so well. There's a lot of things that make him a nightmare to play."
On Wednesday, for a place in the semi-final, Shelton will take on the unseeded Italian Lorenzo Sonego, who ended the run of the 19-year-old qualifier Learner Tien.
The 29-year-old dismissed the American 6-3, 6-2, 3-6, 6-1 to reach the last eight for the first time at one of the four Grand Slam tournaments which take place in Melbourne, Paris, London and New York.
Elsewhere on the ninth day of the season's first Grand Slam tournament, the men's top seed and defending champion Jannik Sinner saw off the 13th seed Holger Rune in four sets and the local hero Alex de Minaur advanced to the quarters.
The 25-year-old, who is seeded eighth, beat the unseeded American Alex Michelsen 6-0, 7-6, 6-3 to reach the last eight in his home Grand Slam tournament for the first time in eight visits.
In the women's draw, two days after annihilating the Briton Emma Raducanu 6-1, 6-0 in 70 minutes in the third round, the second seed Iga Swiatek was even more expeditive in her fourth round tie against the German Eva Lys.
She dispatched the 23-year-old 6-0, 6-1 in 59 minutes to set up a last eight meeting with the eighth seed Emma Navarro.
