Alex de Minaur has survived a gruelling test from plucky Kazakh qualifier Timofey Skatov to safely progress to the US Open second round in New York.
The lowly-ranked Skatov dragged Australia's world No.13 into a baseline dogfight before de Minaur emerged as a relieved 6-2 3-6 6-1 7-5 winner after a near-three-hour battle on Tuesday.
After dropping the second set, de Minaur seemed to find another gear to race through the third and then charge to a 5-2 lead in the fourth.
But after being broken while trying to serve out the match at 5-3, the 13th seed needed to dig deep to avoid being pushed to a deciding fifth set.
A quarter-finalist in 2020, de Minaur next plays China's world No.86 Yibing Wu on Friday (AEST) for a place in the last 32.
Chris O'Connell was Australia's only other winner on day two, crashing countryman Max Purcell's party as Aleksandar Vukic, Thanasi Kokkinakis, Jordan Thompson, Jason Kubler and James Duckworth also bombed out.
Purcell had been riding high after reaching his maiden ATP Masters 1000 quarter-final in Cincinnati, but O'Connell upset the world No.43 to set up a second-round shot at third-seeded former champion Daniil Medvedev.
O'Connell prevailed 6-4 6-3 3-6 7-6 (7-5) in a two-hour, 52-minute battle between the two in-form Sydneysiders.
The 29-year-old O'Connell is also enjoying a breakout season, now projected to climb to a career-high No.61 in the world after also making a run to the last 32 at Wimbledon.
"I know Max really well, I've known him since he was eight," he said.
"I've seen him develop over the years and of late he has been playing some unbelievable tennis.
"There's a load of Australians in the top 100 at the moment, a lot of Australians playing slams so you are bound to draw one now and then.
"Unfortunately I drew Max but at the same time you look at it there's going to be an Australian through to the second round and that is always a positive.
"So once the first point is played I just feel all that goes out the window. I just look across the net and he is just another tennis player from my point of view."
Medvedev conceded only two games in a 6-1 6-1 6-0 first-round rout of hapless Hungarian Attila Balazs.
But the 2021 US Open champion holds no fears for O'Connell ahead of their show-court match-up on Friday (AEST).
"That's going to be exciting," O'Connell said.
"We had a tight battle this year in Doha, I feel I've got a good game style to maybe cause him some trouble. It was very close in Doha.
"I am sure he has a good idea of what I am going to bring and I'm going to play similar to how I did in Doha.
"But he is a top, top player so I am sure he is probably going to change a little bit from that match."
Vukic was beaten 6-4 6-4 6-4 by German 12th seed Alexander Zverev, while Duckworth, a qualifying lucky loser who gained a late reprieve into the main draw, lost 6-4 7-6 (13-11) 6-3 to Brazilian Felipe Meligeni Alvez.
Kokkinakis suffered a shock 6-3 6-4 3-6 6-3 defeat to Taiwan's world No.237 Yu Hsiou Tsu, while Kubler and Thompson both retired with leg injuries a set into their openers.
Kubler was trailing Italian Matteo Arnaldo 6-3 1-0 and Dutchman Botic van De Zandschulp was leading Thompson 6-3.
Australians Ajla Tomljanovic, Daria Saville and Rinky Hijikata are in second-round action on Wednesday.