The 34-year-old beat Serbian Miomir Kecmanovic 6-4 6-3 at the ATP 250 indoor event in Kazakhstan on Monday to set up a clash with second-seeded Italian Luciano Darderi.
While Duckworth advanced, compatriot Aleksandar Vukic put up a tremendous fight before going down in a tight three-setter against world No.79 Adrian Mannarino.
Duckworth, ranked No.73, reached the semi-finals in Winston-Salem in August, then beat Italy's Matteo Arnaldi in the first round of the US Open, but since then hadn't won a singles match.
And victory wasn't a given, with Kecmanovic leading 3-1 in their head-to-head clashes, all played in 2025.
But Duckworth was clinical in the decisive moments against Kecmanovic, who pushed Jannik Sinner to five sets in the first round of Wimbledon.
The Australian saved two break points at 2-2 before breaking for the set at his first opportunity. A 79 per cent first-serve percentage helped keep his opponent at bay.
Duckworth raced to a 3-0 lead in the second set, but Kecmanovic broke straight back. However, he couldn't maintain his momentum and the Aussie broke again before closing out victory on his first match point.
"It was nice to get a win. It's never easy in your first match, just trying to adapt to the conditions,'' Duckworth said.
"Miomir is a great player. I knew I had to play aggressively and not let him dictate as much as I could. Sometimes it's inevitable, but when he's dictating, he's very dangerous. I did a good job of taking my chances and being aggressive.''
After Duckworth's impressive victory, Vukic took the fight right up Mannarino, who won this tournament in 2023.
The Frenchman claimed the first set, before the Australian world No.116 squared the ledger.
In an entertaining match between two aggressive players, Mannarino had two match points on Vukic's serve at 5-2 in the third set, before clinching victory on his own delivery with a service winner.
Mannarino, who lost serve just once in the match, won 7-6 (7-4) 4-6 6-3 to set up a clash with fourth-seeded Russian Andrey Rublev.
The left-handed Frenchman, who lost to Vukic at this event in 2024, was impressive on his serve on Monday, landing 71 per cent of first deliveries and sending down 13 aces in a match that lasted two and a half hours.
Mannarino faces an even bigger challenge in the next round against Rublev, who holds a 4-1 head-to-head advantage.
Australia's Rinky Hijikata, ranked No.86, opens his campaign against another Frenchman, world No.98 Terence Atmane.
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