The 25-year-old started slowly against Germany's Jan-Lennard Struff and looked out of sorts as he dropped the first set on Tuesday. But he gradually put his game back together and won 2-6 6-2 6-2 at the indoor hardcourt ATP 500.
De Minaur converted four of his six break points in the second and third sets. He finished the second with an ace and clinched victory with an overhead smash, winning in an hour 42 minutes.
He will next face Italy's Flavio Cobolli, who beat Spain's Alejandro Davidovich Fokina in straight sets.
It was a welcome return to form for de Minaur after a disappointing defeat to France's Hugo Gaston in the quarter-finals in Antwerp last week.
And BOOM 💥— ATP Tour (@atptour) @alexdeminaur takes the second set 6-2 to force a decider against Struff! @ErsteBankOpen | #ErsteBankOpen pic.twitter.com/swTwZubvEjOctober 22, 2024
"At the end of the day, there's no better measurements than results to see your improvement," de Minaur, who reached a career-high No.6 in the rankings in July, told ATPTour.com.
"I'm very happy with the way my level has improved this year and the types of wins I'm getting. Today was another tough one, so I'm very happy."
Intriguingly, given the injuries which have hampered the world No.10 this year - including having to withdraw from Wimbledon when he was due to face Novak Djokovic in the quarters - he is still in with a chance of reaching the end of year ATP Finals for the first time.
De Minaur is currently ninth in the Live Race To Turin, 265 points behind Russian Andrey Rublev in eighth.
Also in Vienna, Marcos Giron beat fellow American Alex Michelsen to set up a round-of-16 match against top seed Alexander Zverev.
Third seed Stefanos Tsitsipas, Frances Tiafoe, Lorenzo Musetti and Gael Monfils were among the other winners.
However, former US Open champion Dominic Thiem was beaten in his final professional match, losing 7-6 (8-6) 6-2 to Italy's Luciano Darderi.
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The 31-year-old Austrian looked emotional after his first-round defeat on home soil as he received a standing ovation from the crowd.
Thiem announced he would retire this season after being troubled by a wrist injury in recent years.
He won 17 singles titles and reached back-to-back Roland Garros finals in 2018 and 2019, knocking out Djokovic before losing to Rafael Nadal on both occasions.
With agencies
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