The Australian No.2 beat Kamil Majchrzak, Poland's No.1, 3-6 6-3 7-5 in the opening round of the ATP 500 Dubai Open.
Popyrin, like national No.1 Alex de Minaur, sat out Australia's Davis Cup defeat to Ecuador earlier this month, which left Lleyton Hewitt's team facing a relegation play-off with Poland in September.
Victory in this first tour level meeting between the pair should give Popyrin a slight edge should he play Majchrzak then.
The Sydneysider nearly had the chance to establish a double advantage as Poland No.2 Hubert Hurkacz could have been his next opponent. But Hurkacz lost to sixth-seeded Jacob Mensik 6-4 7-6 (9-7) and Popyrin will play the Czech instead.
An early break gave the 56th-ranked Majchrzak a 3-0 lead which he held to take the first set but Popyrin, ranked 47, reeled off five games at the start of the second before taking it 6-3.
The final set went with serve until Popyrin upped the gas in the 11th game breaking to love then serving out.
Popyrin's success contrasted with a trio of Australian losses on the opening day of the Mexican Open.
The headline defeat was that of No.2 seed, and two-time Acapulco champion de Minaur losing 1-6 7-6 (7-4) 6-7 (4-7) to qualifier Patrick Kypson.
Tristan Schoolkate was thumped 6-2 6-2 by Serbia's Miomir Kecmanovic while Adam Walton went down 7-6 (7-1) 7-6 (7-3) to American Aleksandar Kovacevic.
That left James Duckworth and lucky loser Rinky Hijikata to fly the Southern Cross with their round of 32 matches going back-to-back starting at 11am Wednesday AEST. Duckworth plays Czech Dalibor Svrcina and Hijikata Italy's Mattia Bellucci.
The event has continued despite the unrest elsewhere in Mexico following the death of a drug baron known as El Mencho.
The Australian government currently advises "reconsider your need to travel" for the Mexican state of Guerrero in which Acapulco lies.
De Minaur had played a gentle exhibition on the beach in the build-up but was caught cold in the opening set. Kypson, ranked 103 in the world, went on to complete his first tour-level win since Indian Wells in 2024 and third ever.
De Minaur 's last outing was in Rotterdam, when he won the tournament. He was seeking to follow Acapulco titles in 2023 and 2024 and served for the match at 5-4 in the third.
But Kypson, who won four Challenger tournaments last year, broke back and took the tie-break to clinch victory in the pair's first meeting in two hours and 39 minutes..
"It feels amazing," Kypson said. "Everything was important. I had to serve well. I had to return well. I hit my forehand really big. Luckily, I was able to do those things for a pretty extended period of time."
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