World No.1 Jannik Sinner has ruthlessly underlined his US Open title favouritism as he ended the gallant run of Australian Chris O'Connell.
O'Connell was unable to match the heroics of fellow Sydneysiders Alexei Popyrin, Alex de Minaur and Jordan Thompson, who all advanced to the fourth round, as he succumbed 6-1 6-4 6-2 to Sinner in New York on Saturday.
After needing four sets to get through his opener, Sinner has dropped just 13 games in his past two matches, at an average of only two a set.
The Australian Open champion was particularly clinical on serve, crunching down 15 aces, not offering up a single break point for the entire match and winning 82 per cent of points after landing his first delivery.
"Day by day I feel like my level has been better, so happy about that. Let's see what's coming the next round," Sinner said.
The Italian isn't taking anything for granted after the shock eliminations of defending champion Novak Djokovic and third seed Carlos Alcaraz, his two chief threats for the title.
"It shows that this sport is unpredictable," Sinner said.
"Whenever you drop a little bit of your level, if it's mental, if it's tennis-wise or physical, at the end it has a huge impact on the result.
"Both opponents who they lost against, they played some incredible tennis, and it happens.
"So I just watch on my side what I have to do. Then we will see what I can do."
O'Connell admitted feeling "a little bit clueless" in the face of the Sinner onslaught.
"The best tennis player I've ever played, for sure," the 30-year-old O'Connell said.
While Sinner next faces American 14th seed Tommy Paul, a four-set winner over Canadian qualifier Gabriel Diallo, for a place in the quarter-finals, O'Connell can console himself with a career-best payday of $US215,000 ($A$315,000) for reaching the last 32.
The only past men's US Open champion still standing is 2021 winner Daniil Medvedev, who beat No.31 Flavio Cobolli 6-3 6-4 6-3 in the late night match.
Medvedev, the No. 5 seed, will face Nuno Borges, who was a point away from elimination at 6-3 in a fourth-set tiebreaker, then rallied to beat Jakub Mensik 6-7 (5-7) 6-1 3-6 7-6 (8-6) 6-0.
"I said it before the match that to me upsets don't really matter. The conditions are a bit tricky," Medvedev said.
"The favourites maybe have less margin against the other guys. Just have to be more cautious. If I play good tennis I can win the whole thing.
"If I don't play good I can lose against anyone. I just have to play my best and try to win."
Popyrin will take on explosive American Frances Tiafoe on Sunday (Monday AEST) for a quarter-final berth after blowing the bottom half of the draw wide open with his stunning 6-4 6-4 2-6 6-4 disposal of Djokovic.
De Minaur and Thompson set up an all-Australian fourth-round clash as de Minaur ousted British veteran Dan Evans 6-3 6-7 (4-7) 6-0 6-0 and Thompson accounted for 30th seed Matteo Arnaldi 7-5 6-2 7-6 (7-5).
Brit Jack Draper, meanwhile, equalled his best run at a grand slam by ousting Alcaraz's conqueror Botic van De Zandschulp in straight sets.
Draper matched his effort in New York from last year with a 6-3 6-4 6-2 third-round victory.
The 25th-seeded Draper will play Thomas Machac for a quarter-final berth after the Czech crushed Belgian qualifier David Goffin 6-3 6-1 6-2.
