In the wake of upset losses by No. 3 Carlos Alcaraz and No. 2 Novak Djokovic, men's world No. 1 Jannik Sinner advanced comfortably into the second week of the US Open on Saturday.

Sinner enjoyed a businesslike 6-1, 6-4, 6-2 win over Australia's Christopher O'Connell to reach the round of 16, where he will face either Canadian qualifier Gabriel Diallo or American Tommy Paul, the No. 14 seed.

Sinner ensured that dubious history was not made Saturday at Flushing Meadows; since the start of the Open era in 1968, there has never been a US Open without any of the men's top three seeds in the round of 16.

"I try to stay on my side of the net and I'm trying to take it day by day," Sinner said in his on-court interview. "Each opponent is a very tough challenge. There have been already a couple of upsets, so let's see what's coming, but I'm very happy to be still here."

After slow starts in his opening two matches, Sinner shot out of the blocks at Arthur Ashe Stadium for a 5-0 lead before taking the first set on serve. He broke early for a 2-1 lead in the second and went on to clinch the set with a vicious cross-court forehand winner.

Sinner fired 15 aces for the match and did not face a break point. He finished with 46 winners.

In the first men's match Saturday, Tomas Machac won 6-3, 6-1, 6-2 against David Goffin and moved into the fourth round at a major for the first time.

Meanwhile, unseeded Botic Van de Zandschulp, who knocked out Alcaraz in the second round, lost to Britain's Jack Draper 6-3, 6-4, 6-2.

ESPN Stats & Information and Reuters contributed to this report.