Carlos Alcaraz was given a scare by Australian qualifier Li Tu in the first round of the US Open on Tuesday before going on to seal a 6-2, 4-6, 6-3, 6-1 victory in New York.
Four-time Grand Slam champion Alcaraz, who lost to Novak Djokovic in the final of the Paris Olympics, got off to a hot start before errors began to pile up and he dropped the second set.
The Spaniard restored order by whipping a forehand to break in the third set for a 4-3 lead and never looked back, claiming the victory with his eighth ace to set up a second-round meeting with Dutch player Botic Van De Zandschulp.
Tu, an Adelaide native who stepped away from tennis in 2014 for six years to get a degree and start a tennis academy, won three qualifying matches to earn his first appearance on Arthur Armstrong Stadium court against the third seed.
"Obvious he surprised me a little bit," Alcaraz said in an on-court interview with ESPN.
"He started the match a little nervous but after the first set he grew up, he started to play great tennis.
"Now I'm going to follow him and his results because I'm pretty sure I'm going to be seeing him around very, very soon."
Alcaraz, who showed no signs that his movement was limited by a right ankle injury he suffered during a practice session Saturday. won the first set with ease and the subdued crowd appeared to resign itself to a one-sided match.
However, Tu turned the tables with a passing shot that flew by the charging Alcaraz for a 5-4 lead in the second and broke serve with a beautiful one-handed backhand down the line to level the contest, raising his hand to his ear as the crowd came to life.
Alcaraz's power began to wear Tu down in the third set in hot and humid conditions, and the 21-year-old went on to claim the win before thanking the fans for creating an "electric" atmosphere.
"It's one of the most electric courts, electric crowds that I have played in front of," he said.
"It's an honor to step on this court and have the people enjoy my tennis once again."
Alcaraz won the French Open in June and defeated Djokovic to triumph at Wimbledon a month later but was left disappointed after falling short at the Paris Games before suffering a shock defeat to Gael Monfils at the Cincinnati Open. If he can add another US Open title to the one he captured in 2022, Alcaraz would join Rod Laver (1969) and Rafael Nadal (2010) as the only men to capture those three Grand Slam titles in the same year during the Open era.
On Tueaday, he joined Nadal as the only men in the Open era to win a match in each of his first 15 major appearances. Nadal won a match in each of his first 34 major appearances before losing in the first round at Wimbledon in 2013.
Elsewhere in men's first-round action Tuesday, No. 11 Stefanos Tsitsipas' US Open woes continued as he suffered a 7-6 (5), 4-6, 6-3, 7-5 defeat to Thanasi Kokkinakis.
After losing a close first set in a tiebreaker, Tsitsipas rallied to win the second and level the match, but he appeared to be bothered by an abdominal issue.
Tsitsipas, a two-time Grand Slam finalist, has never made it past the third round at Flushing Meadows.
He also struggled leading up to the tournament, winning just one of his three matches at the Canadian Open and the Cincinnati Masters.
For Kokkinakis, it was his first win at the US Open since 2019.
"I had a five-set battle with him a couple of years ago at the Australian Open, and I was expecting a war," Kokkinakis said in his postmatch on-court interview. "It was physical out there, and I have a tendency to sometimes drag these matches on and have some real long battles, but I just tried to stay focused, stay the course and just tried to play every point."
He will next face Nuno Borges, a straight-sets winner over Federico Coria.
Jannik Sinner, the No. 1 seed on the men's side, played his opening-round match at Arthur Ashe Stadium and emerged with a 2-6, 6-2, 6-1, 6-2 win over Mackenzie McDonald. It was Sinner's first action since word emerged that he had failed two drug tests in March but escaped suspension.
Fifth seed and former US Open champion Daniil Medvedev overcame a second-set wobble to beat unseeded Dusan Lajovic 6-3, 3-6, 6-3, 6-1.
"Tough match. Dusan did play well," Medvedev said. "The first two sets he was playing really well. I'm happy that I managed to keep my level. In the second set, I feel like I played really well, he just played better. I kept my level. He dropped a little bit third and fourth set. I managed to play better and better from that."
Medvedev owns a 27-0 record after winning the first set at the US Open, the most wins without a loss by any man in the Open era (since 1968).
In other men's results, France's Arthur Fils beat American Learner Tien 6-4, 3-6, 6-1, 6-2.
No. 19 Felix Auger-Aliassime was knocked out in the first round by 18-year-old Jakub Mensik, and No. 7 Hubert Hurkacz and No. 30 Matteo Arnaldi were among the men's winners.
No. 25 Jack Draper reached the second round after his opponent, Zhang Zhizhen, retired due to a left leg injury in the third set with the Briton leading 6-3, 6-0, 4-0.
No. 10 Alex De Minaur of Australia showed he is fully recovered from the hip injury that forced him to withdraw from the Paris Games last month by beating American Marcos Giron 6-3, 6-4, 5-7, 6-4, while No. 16 Sebastian Korda defeated France's Corentin Moutet 7-6 (3), 6-1, 6-0.
Stan Wawrinka failed to make the most of his main-draw wild card as the three-time Grand Slam champion lost 6-4, 7-6 (5), 6-3 to Mattia Bellucci.
No. 14 Tommy Paul topped Lorenzo Sonego 6-4, 6-2, 5-7, 6-2 in the final match of the night.
The Associated Press and Reuters contributed to this report.