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The top seed and 2023 Vienna champion overwhelmed Altmaier from the outset with his heavy ball-striking and imposing pace, racing to the finish in just 58 minutes. Sinner, who was forced to retire from the third round of his Shanghai title defence earlier this month, extended his winning streak on indoor hard courts to 17 matches.

“I feel like in the first set everything was working very well,” Sinner said. “On indoor courts, you have to be very careful. If your opponent starts to serve well, it’s very difficult to break. But I’m very happy about today’s performance, starting the tournament in a very positive way, not only game-wise but feeling wise.”

Sinner’s previous fastest win of the season came in his opener in Cincinnati, where he blitzed Daniel Elahi Galan in 59 minutes. Against Altmaier at the ATP 500 event in Vienna, the 24 year-old Italian hit 19 winners to just seven unforced errors and did not face a break point, according to Infosys ATP Stats.

After improving to 29-0 in the opening rounds since Cincinnati in 2023, Sinner will next meet countryman Flavio Cobolli, who moved past Tomas Machac 7-6(6), 6-2.

Last week’s Almaty champion Daniil Medvedev overcame Nuno Borges 6-4, 6-7(7), 6-2 to keep alive his late-season push to qualify for the ATP Finals. 

After letting slip two match points in the second-set tie-break, Medvedev regrouped in impressive fashion to begin his title bid in Vienna, where he last lifted the trophy in 2022.

The former ATP Finals champion is 13th in the ATP Live Race To Turin and could meet eighth-placed Lorenzo Musetti in a blockbuster quarter-final clash in Vienna. First, Medvedev faces a rematch of the Almaty final against Corentin Moutet, who earlier eased past qualifier Damir Dzumhur 6-3, 6-0.

Earlier, Tallon Griekspoor became the first Vienna quarter-finalist by edging Brandon Nakashima 7-6(4), 7-6(2) with a clutch display.