Opportunity knocks for Alexei Popyrin after the Australian young gun surged into the second round of the US Open for the first time.

Popyrin, who only turned 20 this month, downed the vastly more experienced Federico Delbonis 6-1 7-5 7-6 (7-5) to notch yet another milestone in a breakout season for the former French Open junior champion.

After cracking the world’s top 100 for the first time, then earning direct entry into a major for the first time, Popyrin has now reached at least the second round at all four grand slams in 2019.

He didn’t have it easy, though, on Tuesday.

After breezing through the opening set in 23 minutes, Popyrin had to battle back from service breaks down in the second and third to keep the Argentine at bay.

Sporting matching T-shirts displaying “Pop on Top”, Popyrin’s parents rode every single point before their son indeed finished on top in a tick over two hours.

His reward is a meeting on Thursday with Mikhail Kukushkin after the Kazakh removed 10th-seeded Wimbledon semi-finalist Roberto Bautista-Agut from Popyrin’s passage to the last 32 in New York.

Should he cash in on his good fortune, Popyrin could face countryman Jordan Thompson for a spot in the second week.

Thompson’s 6-3 6-2 6-4 victory over Joao Sousa booked Popyrin’s fellow Sydneysider a second-round date with Italy’s 24th seed Matteo Berrettini, who ousted Richard Gasquet 6-4 6-3 2-6 6-2.