World No. 1 Jannik Sinner faces a tricky test on Monday night against Alexander Bublik.

Sinner has hardly put a foot wrong at the 2025 US Open, but Bublik represents a unique challenge for the defending champion and tournament favorite.

Not only is Bublik one of the most talented players on tour, but he’s got a decent head-to-head record against the Italian. Sinner has won four of the six meetings between the two, but Bublik has won two of the last three encounters, including their most recent tussle at ATP Halle in June.

Nevertheless, Sinner is a -1400 favorite to advance past Bublik and into the quarterfinals.

Barring something unforeseen like injury or illness, we have a pretty good idea of what to expect when Jannik Sinner takes the court these days.

Sinner is remarkably consistent when he’s serving, and his defensive game is on the same level as Novak Djokovic’s during the Serb’s prime. In other words, there’s no weakness to pick apart in Sinner’s game right now, which means you’re going to need to be better than him on the day to have a chance.

For almost every player on the ATP Tour, that’s a non-starter. There are a select few, however, who have the ceiling to stand in the ring with the four-time Grand Slam champion.

Alexander Bublik happens to be one of those players. The problem is, you never have any idea what to expect when the Kazakh walks onto the court.

Against weaker opponents, that variance makes Bublik a tough player to back. Generally, you want to stay away from backing the 28-year-old as a favorite because there’s always a decent chance he just isn’t feeling it that day.

But when he’s an underdog, especially a big one, he becomes quite intriguing because if he is focused, he can be unplayable.

Furthermore, Bublik is incredibly difficult to gameplan for, because you never know what tricks he’s going to pull out of his sleeve. He’ll mix in some underhand serves, go to the net when you least expect, and try to smash winners out of nowhere.

A gifted athlete blessed with a massive wingspan, Bublik’s court coverage gives him a terrific foundation, but he really dines out on his serve.

Sinner can handle elite serves better than just about anybody in the sport, but Bublik’s offering is all-world, and will keep him in this match so long as he’s on rhythm.

If that is the case, there’s certainly a chance that Bublik finds a foothold in this match, which is all you’re really asking out of a +800 underdog.

It’s not a bet you should expect to win, but a sprinkle on Bublik to pull the upset isn’t a terrible idea.

The Play: Bublik +800 (bet365)

Michael Leboff is a long-suffering Islanders fan, but a long-profiting sports bettor with 10 years of experience in the gambling industry. He loves using game theory to help punters win bracket pools, find long shots, and learn how to beat the market in mainstream and niche sports.