NEW YORK -- Jannik Sinner never gave his third-round opponent at the US Open on Saturday, Christopher O'Connell, even a moment to contemplate pulling off the sort of monumental upset that eliminated Novak Djokovic and Carlos Alcaraz.
"It shows that this sport is unpredictable. 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," Sinner said. "Both opponents who they lost against, they played some incredible tennis. And it happens."
Not to the No. 1-ranked Sinner, who is suddenly the favorite to win the men's championship at Flushing Meadows. He won the first five games and 21 of the first 29 points to make quite clear how things would go at Arthur Ashe Stadium and wrapped up a 6-1, 6-4, 6-2 victory over O'Connell in under two hours.
"I felt like he was on from the get-go," O'Connell said. "I felt a little bit clueless, to be honest. ... Every single shot, I just felt like I had to do something with it, because he was just on me. He was suffocating me."
Stepping on court less than 15 hours after Djokovic's loss to Alexei Popyrin and two days after Alcaraz's loss to Botic van de Zandschulp, Sinner was as dominant as can be in every facet. With 23-time major champion Serena Williams watching from an Ashe suite, Sinner struck 15 aces. He never faced a break point. He won five of O'Connell's 12 service games. He finished with more than twice as many winners, 46, as unforced errors, 22.
"The best tennis player I've ever played, for sure," the 30-year-old O'Connell said.
The only past men's champion at the US Open still in the bracket, 2021 winner Daniil Medvedev, defeated No. 31 Flavio Cobolli 6-3, 6-4, 6-3. 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), 6-1, 3-6, 7-6 (6), 6-0.
"For sure didn't expect to have this in the fourth round when Novak and Carlos are here," Medvedev said of the remaining field. "So, it's a fun feeling from one side, but from the other side it's a new tournament. I need to play my best to try to win it again."
Borges is the second Portuguese man since the Open era began in 1968 to make the round of 16 in New York, joining João Sousa in 2018. Borges played college tennis at Mississippi State and was the ITA National Player of the Year in 2019. He's one of two former college players left on the men's side, along with Brandon Nakashima (Virginia).
Since losing the first set he played in New York, against Mackenzie McDonald -- which also was the first set Sinner had played since news emerged of a doping case that involved two positive tests in March for trace amounts of a banned anabolic steroid -- the 23-year-old from Italy has performed impeccably, dropping a total of 18 games across nine sets.
Trying to collect his second Grand Slam title of the year after gaining the first of his career at the Australian Open in January, Sinner will face No. 14 Tommy Paul of the United States in the fourth round on Monday. Paul defeated Canadian qualifier Gabriel Diallo 6-7 (5), 6-3, 6-1, 7-6 (3).
"He's a great mover. He has improved a lot in the last period of time. It's going to be a tough challenge," Sinner said about facing Paul, a 2023 Australian Open semifinalist. "He plays some great tennis, especially here in America."
"We've had some great matches," Paul said. "I remember I played him on clay, had some match points against him. Then the last match, I think it was in Toronto, he played awesome. I didn't feel like I did too much wrong. He kind of took the racket out of my hands. I'm definitely going to try and, you know, make it uncomfortable for him."
Perhaps there was wariness on Sinner's part heading into Saturday, given recent events. This is only the third time in the Open era (the others were in 1973 and 2000) that two of the top three-seeded men were gone before the fourth round.
So Sinner woke up as the man considered likeliest to win the US Open, a status that belonged to No. 3 Alcaraz -- the champion at the French Open and Wimbledon this season -- before the tournament began. No. 2 Djokovic -- the defending champ and owner of a men's-record 24 major trophies -- moved atop the odds when Alcaraz was sent home Thursday night, only to relinquish that after his own early exit Friday night.
The 87th-ranked O'Connell harbored hope of producing yet another surprise, even if he's never beaten a member of the top 10 or been past the third round at a Slam.
What Van De Zandschulp and Popyrin did allowed O'Connell to dream of producing something similar against Sinner.
"I felt like he was on from the get-go. I felt a little bit clueless, to be honest. ... Every single shot, I just felt like I had to do something with it, because he was just on me. He was suffocating me."Christopher O'Connell on facing Jannik Sinner at US Open
"I mean, yeah, I've got to believe," O'Connell said, "but I just felt that he was really on fire."
There is something quite difficult about trying to follow up one career-best win with another, and Van De Zandschulp didn't really show up on Saturday, eliminated by No. 25 Jack Draper 6-3, 6-4, 6-2. Draper, a 22-year-old left-hander from Britain, never has been past the fourth round a major, and neither has his next opponent, unseeded Tomas Machac, a 6-3, 6-1, 6-2 winner against David Goffin.
"After the match [against Alcaraz], it was a little bit crazy," Van De Zandschulp said. "You try to think about the next match but you get reminded a lot of the match the day before. So of course it was tough to play today after the last two days."
In other men's singles results from Saturday, Jordan Thompson of Australia took down Italy's Matteo Arnaldi, the No. 30 seed, 7-5, 6-2, 7-6 (5).
ESPN Stats & Information and The Associated Press contributed to this report.