New York (AP) – Frances Tiafoe beat the 22-time major champion 6-4, 4-6, 6-4, 6-3 in the fourth round of the US Open to end Rafael Nadal’s 22-match winning streak at the Grand Slam tournament.

Tiafoe, a 24-year-old from Maryland, seeded 22nd at Flushing Meadows, reached the second major quarterfinals of his career. He’s the youngest American player to ever appear at the US Open since Andy Roddick in 2006, but it wasn’t a case of a one-sided rush, supporting his own. Nadal is almost as popular as he is in tennis and has heard considerable support at Arthur Ashe Stadium as the volume increased after the retractable roof closed in the fourth set.

“I don’t even know what to say right now. I’m beyond happy. I can’t believe it.” Said Tiafoe, who will now face No. 9 Andrey Rublev. “He’s one of the greatest ever. I played incredible tennis today, but I don’t even know what happened.”

Here’s what happened: Tiafoe outperformed No. 2 seed Nadal. More surprisingly, he also returned better. And he kept his cool, stayed in the moment and never let the stakes or the opponent get to him. Nadal had won both his previous matches, and he won every set as well.

“Well done for him,” Nadal said. “He was better than me.”

The surprise came a day after one of Tifo’s friends, Nick Kyrgios, eliminated No. 1 seed and defending champion Daniil Medvedev. Nadal won the Australian Open in January and the French Open in June. He then made it to the semifinals at Wimbledon in July before pulling out of the tournament due to abdominal pain; That doesn’t go into the books as a loss, as he was knocked out before the match.

The 36-year-old from Spain competed only once in the 1 1/2 months between leaving the All England Club and arriving in New York while recovering from that injury. His game has not been up to his usual standards at the US Open, which he has won four times, especially in his serve.

Nadal changed his serve motion, tossing the ball lower than usual so as not to put too much pressure on his midsection while reaching with the racket. There were many signs on Monday that his service was not in tip-top shape: nine double-faults, a firs served percentage of around 50%, five breaks by Tiafoe.

The next-to-last break came in the fourth set for a 4-3 lead, when Nadal slammed a backhand into the net, and Tiafoe slid backwards toward the sideline for the ensuing change, his fist raised. Fifteen minutes later, Tiafoe broke again, and it was over.

When one last backhand from Nadal found the net, Tiafoe put his hand on his head. As he sat in his sideline chair, he buried his face in a towel.

Earlier in the tournament there were signs of trouble for Nadal. He lost the first set of his firs round match. He did the same in the second round, when he accidentally cut the bridge of his nose and found himself dizzy when the edge of his racket frame jumped off the court and caught him in the face at a backhand follow-through.