Daniil Medvedev dropped just four games as he breezed past Nuno Borges to secure his place in the US Open quarter-finals.
Russia’s Medvedev, champion in New York three years ago, was barely troubled by the Portuguese in a 6-0 6-1 6-3 win.
Medvedev is the only former US Open champion left in the draw in New York, and the only Grand Slam singles champion other than Jannik Sinner.
He could potentially face world number one Sinner – who beat him from two sets down in the Australian Open final in January – next.
It is the fifth time in the past six years that Medvedev has reached the last eight at the US Open.
Medvedev was interviewed on court afterwards by Nick Kyrgios, who was the last player to beat him before the quarter-final stage.
“The last time I lost in the fourth round was against you, right? Good memories,” the 28-year-old joked.
“I try to work hard. Sometimes I do, sometimes I don’t.
“I have the mentality that if the other guy practises more than me, I have less chances to win, and I want to win all the time.”
Medvedev was broken just once in the match, as he went down 2-1 in the third set, before play was delayed after a fire alarm went off in the building where the electronic line calling team is.
The US Open does not have line judges, with all the calls made by the Hawkeye technology.
The building was evacuated, leading to a brief pause in play, before fifth seed Medvedev immediately broke back and won five of the next six games to advance.
Sinner faces Tommy Paul in the night session on Arthur Ashe later on Monday.
Britain’s Jack Draper earlier advanced with an impressive straight-set victory over Tomas Machac to reach his first Grand Slam quarter-final.