Carlos Alcaraz’s 15-match Grand Slam unbeaten run ended at the U.S. Open with a sloppy 6-1, 7-5, 6-4 loss to 74th-ranked Botic van de Zandschulp in the second round Thursday night, a stunning result that eliminated the tournament favorite.

This one was hard to predict, given Alcaraz’s standing in the game, his excellence of late and his opponent’s far-lesser résumé.

Alcaraz won the French Open in June and Wimbledon in July to raise his career total to four major championships, including taking the title at Flushing Meadows in 2022.

But he never found his footing against van de Zandschulp, a 28-year-old from the Netherlands. Alcaraz was way off, repeatedly missing the sorts of shots he usually makes routinely. After double-faulting to fall behind two sets to none — a deficit he’s never overcome — the No. 3-seeded Alcaraz slung his equipment bag over this shoulder and trudged toward the locker room.

Glancing in the direction of his coach, 2003 French Open champion Juan Carlos Ferrero, Alcaraz pointed his right index finger at his temple, then wagged that finger, as if to say, “I’m not thinking straight.”

He might have been excused for being confused by what was transpiring under the closed retractable roof at Arthur Ashe Stadium on a chilly evening.

The 21-year-old from Spain came in with a 16-2 record at the U.S. Open, where he never lost before the quarterfinals in three previous appearances. This also was Alcaraz’s earliest defeat at any major tournament since bowing out in the second round of Wimbledon in 2021 as a teenager; he’s never lost in the first round at a Slam event.

In contrast, van de Zandschulp only once has been to a Grand Slam quarterfinal, getting that far at the U.S. Open in 2021.

Otherwise, he is not someone most folks would have expected to pull off this sort of upset. Consider: Van de Zandschulp was just 11-18 for the season at the start of this week and hadn’t won consecutive matches at a tour-level event this year.

“Actually, I am a little bit at a loss for words,” he said. “It’s been an incredible evening for me.”

Sure was.

The key stat probably was that van de Zandschulp won the point on 28 of 35 trips to the net.

The opening set was unbelievably lopsided. With van de Zandschulp’s powerful forehands and serves at up to 132 mph finding their marks, Alcaraz never seemed to get comfortable — even though he won their past two matchups.

Alcaraz did not produce a single winner in that set and was nearly doubled up in total points, 24-13. The second set was a bit better for him, but not enough so, and a double-fault gift-wrapped a service break that put van de Zandschulp up 6-5. When Alcaraz pushed a forehand wide to end the next game, van de Zandschulp finished off a hold at love that gave him the initial two sets after 1½ hours of action.

It didn’t take long for Alcaraz to fall behind by a break in the third too, at 3-2, but he made a stand immediately — well, with some help, because van de Zandschulp’s double-fault ceded a break that made it 3-all. Alcaraz then held at love and smiled as he strutted to the changeover.

That grin quickly was gone, though, because Alcaraz’s mistakes kept arriving, and van de Zandschulp never folded.

“Of course I had some nerves, but I think if you want to beat one of these guys, you have to keep your calm and keep your head there,” said van de Zandschulp, who will face No. 25 seed Jack Draper of Britain in the third round Saturday. “Otherwise, they take advantage of it.”