Jannik Sinner advanced to the Round of 16 of the US Open on Saturday. That usually isn’t big news for a No. 1 seed, but after what happened in the third round, nothing can be taken for granted.

The Italian defeated unseeded Australian Christopher O’Connell 6-1, 6-4, 6-2 at Arthur Ashe Stadium, dominating an overmatched opponent in just under two hours. He posted 46 winners to O’Connell’s 18, plus 15 aces, and didn’t even allow a break point.

And yet, his most impressive point might have been one he lost.

The win leaves Sinner as the favorite to win the tournament at +125 odds on BetMGM. While he was the tournament’s top seed, both No. 3 Carlos Alcaraz and No. 2 Novak Djokovic entered with better odds, which wasn’t a surprise given they had won every Grand Slam in the past two years save for Sinner’s victory at the 2024 Australian Open.

And then, well, the entire tournament went sideways.

On Thursday, Alcaraz went down against the unseeded Botic van de Zandschulp in one of the biggest upsets in recent tennis history. The most electric player in tennis looked unplugged from the start and ended up losing in straight sets.

In a sport where the elites rarely lose to the non-elites in Grand Slams, that was an enormous development. Then Djokovic lost as well, to No. 28 Alexei Popyrin. The loss left the Serbian without a Grand Slam in a year for the first time since 2017, and also broke a streak of him, Roger Federer and Rafael Nadal winning at least one Slam every year since 2002.

“It shows how tennis is. It’s very unpredictable. When you drop just a small percentage, the outcome is big,” Sinner told ESPN after his match.

The 2024 US Open will also be the first Grand Slam without the Big 3 in the Round of 16 since the 2004 French Open, a streak of 81 tournaments.

So Sinner is left, with No. 4 Alexander Zverev (+350) and No. 5 Daniil Medvedev (+400) as the remaining top dogs. Next is No. 12 Taylor Fritz at +1200, which would make him the first American man to win a Grand Slam in singles since Andy Roddick at the 2003 US Open.

It’s a good position for Sinner to be in, especially after he entered the tournament under a cloud of controversy stemming from his two positive tests for a banned anabolic steroid. The 23-year-old avoided a suspension after his camp convinced the International Tennis Integrity Agency the drug entered his system through a massage.

Not everyone, including US Open commentator Nick Kyrgios, was convinced it was the right call.