The U.S. Open is moving ahead without two of tennis’ biggest stars after Carlos Alcaraz and Naomi Osaka lost their respective matches on Thursday.

They were both defeated in the second round of the New York-based tournament, which runs through Sept. 9 and is the last of the year’s four Grand Slams.

Alcaraz’s exit is especially surprising, as the third-ranked male tennis player in the world has never lost before the quarterfinals in any of his previous three appearances at the U.S. Open.

In fact, the Associated Press notes, he hasn’t been defeated this early at any major tournament since bowing out of the second round of Wimbledon in 2021. The Spanish 21-year-old won the French Open in June and Wimbledon in July, as well as a silver medal in the Paris Olympics.

But his 15-match Grand Slam winning streak screeched to an abrupt halt this week thanks to a much lesser-known player, No. 74-seeded Botic van de Zandschulp of the Netherlands.

The Dutchman, 28, beat Alcaraz in straight sets: 6-1, 7-5, 6-4. It was a particularly triumphant victory for a player who has only made it to one Grand Slam quarterfinal in his career — at the 2021 U.S. Open — and publicly contemplated retirement earlier this year.

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

He will face No. 25 Jack Draper of the United Kingdom in the third round on Saturday.

Analysts say Alcaraz seemed off his game from the start, missing shots he normally makes, racking up back-to-back unforced errors (27) and hitting an uncharacteristically low number of winners (21).

Alcaraz, who won the U.S. Open men’s singles title in 2021, acknowledged at a post-game press conference on Thursday that he hadn’t brought as much energy to the match as he would have liked, saying the brief break he took after the Olympics “probably … wasn’t enough.”

He has lost three of his four matches since returning from Paris, including in the opening round of the Cincinnati Open earlier this month — which saw the typically upbeat player repeatedly smash his racquet in frustration (and later apologize). Alcaraz also cut a recent practice session short after twisting his ankle, the Washington Post reported.

But he took responsibility for his shortcomings, telling reporters it had been a “fight against myself, in my mind, during the match” and crediting van de Zandschulp for playing well.

“He didn’t make a lot of mistakes that I thought he was going to do, so I was confused a little bit,” Alcaraz said. “I didn’t know how to manage that, how to deal with it. I couldn’t increase my level.”

Osaka’s U.S. Open comeback dreams were cut short

Naomi Osaka hits during the women’s singles second round at the U.S. Open on Thursday.

Charly Triballeau/AFP via Getty Images

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Charly Triballeau/AFP via Getty Images

For Osaka, it was more of a surprise that she made it to the second round in the first place.

The world No. 88 in women’s singles — who was once ranked first — is relatively fresh off two hiatuses, which she took in 2021 for mental health reasons and in 2022 following the birth of her daughter.

The 26-year-old Japanese player has won four Grand Slams, including two U.S. Open women’s singles titles (in 2018 and 2020), but has yet to go further than the second round at any major tournament since her return to the court.

She entered Thursday’s match with momentum, helped by some show-stopping custom outfits and an energizing first-round win.

She defeated No. 10 seed Jelena Ostapenko of Latvia on Tuesday, 6-3, 6-2. It was her first win against a top 10 opponent in four years, and clearly an emotional experience, as Osaka could be seen wiping tears away afterward.

Osaka played a competitive match against No. 52-ranked Karolina Muchova, but it wasn’t enough. The Czech player stood her ground — even in a tense tiebreaker — to win 6-3, 7-6 (5).

Muchova, 28, reached both the French Open final and U.S. Open semifinals in a banner 2023 season, but was sidelined by a wrist injury for 10 months and only returned to the circuit in June. She will play Russia’s Anastasia Potapova on Saturday.

Osaka said after the match that she felt nervous during high-pressure moments, and suggested she needed to play more matches on big stages to get used to that feeling. She said she was proud of herself for getting so far, but still takes losses like Thursday’s personally.

“It’s like a dramatic word, but I feel like my heart dies every time I lose,” she said. “It sucks a lot, but I’ve been trying to be more mature and learn and talk more about them.”