Alex de Minaur has blown his best opportunity to claim a maiden grand slam crown after crashing out in the US Open second round in New York.

Australia’s world No.7 slumped to a shock straight-sets loss to Botic van de Zandschulp, a Dutchman he’d beaten in all four of their previous meetings.

In a demoralising display, de Minaur dropped serve five times and only broke his 70th-ranked opponent once in a 6-4 7-5 6-2 defeat on Thursday (local time).

He also racked up 30 unforced errors compared to just 23 winners in the two-hour, 43-minute upset on The Grandstand.

A three-times US Open quarter-finalist, including on his past two visits to Flushing Meadows, de Minaur had been the fourth-highest-ranked player left in the draw following the exits of Novak Djokovic and Felix Auger-Aliassime.

His Italian nemesis and world No.1 Jannik Sinner, who holds a 13-from-13 record over the Australian, is also missing with a knee injury, while defending champion Carlos Alcaraz is playing his first tournament in four months.

But the sixth seed was unable to cash in.

De Minaur was almost disconsolate following his Wimbledon quarter-final loss to Flavio Cobolli in July. He will likely be equally as devastated after suffering his earliest defeat in New York in five years.

De Minaur’s shock departure incredibly leaves unheralded wildcard Dane Sweeny as Australia’s last player standing at the season’s final grand slam event.

Sweeny will play 21st seed Luciano Darderi on Saturday (Sunday AEST) for a most improbable spot in the last 16 after taking out Darderi’s world No.14 compatriot Lorenzo Musetti 3-6 6-1 6-2 6-2 in a second-round boilover earlier on day six.

-AAP