158 mph?! Hawk-Eye throws cold water on Ben Shelton's apparent record serve at US Open

Ben Shelton is known for his lightning-fast serve — just maybe not that fast.

During the third set of the 23-year-old's thrilling US Open semifinal victory over fellow American Frances Tiafoe, Shelton appeared to record a eyebrow-raising, 158 mile-per-hour serve, according to the measurement displayed in the stadium.

It was, certainly very fast: Tiafoe was barely able to get his racket on the potentially record-breaking serve, sending the return out of bounds as a result of the rapid speed.

However, 158 mph immediately felt a little bit too high, even for a serve that was clearly hit with a lot of power. That number would have broken several records, becoming the fastest serve ever officially recorded by the ATP.

Unfortunately, the record was taken back quickly, thanks to computer visual system Hawk-Eye. Both Hawk-Eye and the U.S. Tennis Association (USTA) confirmed the serve hit only 144 mph, via The Athletic's Lukas Weese .

The US Open later corrected the mistake on social media.

A 144-mph serve is not nothing: It's still faster than a lot of current players on the tour can hit. But it's a speed that Shelton's serves hit on a regular basis, and it wasn't even his fastest of the night, with the young American clocking a serve at 149 mph earlier in the match.

Shelton's serves, in general, were noticeably faster than Tiafoe: The 23-year-old averaged 119 mph on his serves through the first three sets, while Tiafoe averaged 104 mph. Shelton's superior serve led him to victory in four sets, advancing to his first Grand Slam final behind a whopping 20 aces, including eight in the fourth set alone.

As for his serve speed, Shelton has cracked 150 mph in other events, so 158 might be coming — just not on Friday.