Carlos Alcaraz's 15-match grand slam unbeaten run has ended at the US Open with a sloppy 6-1, 7-5, 6-4 loss to 74th-ranked Botic van de Zandschulp in the second round.

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, and was the pre-tournament favourite to leave with the trophy again.

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 number three-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 dismissively.

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 US Open, where he never had been eliminated before the quarterfinals in three previous appearances.

This also was Alcaraz's earliest loss 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.

The opening set Thursday was unbelievably lopsided. With van de Zandschulp's powerful forehands and serves at up to 212kph finding their marks, Alcaraz never seemed to get comfortable — even if he had won their past two match-ups.

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 1.5 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 — with some help, as 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 smile was quickly gone, though, because Alcaraz's mistakes kept arriving, and van de Zandschulp never folded.

AP