New York: The US Open's Sunday start gives some players a chance to get a nice head start. For Novak Djokovic, it turned into a stunning head start back to the airport.The 24-time Grand Slam champion was knocked out in the first round of the US Open for the first time, beaten by Mariano Navone of Argentina 7-6 (5), 5-7, 4-6, 6-2, 6-1.Djokovic was 19-0 in the US Open first round and hadn't lost his opening match in any major since the 2006 Australian Open.Also Read: US Open boosts record prize money, rejects revenue-share push"It's a good record, another one. But yeah, I'm not really thinking about it," Djokovic said. "Of course, I've been very proud of all the achievements in the past, but now is now."And now the No. 4 seed and four-time champion in Flushing Meadows looks every bit of his 39 years, vomiting and battling leg problems during a match that lasted more than 4 1/2 hours."Now I have to recover," Navone said. "It's almost 12 o'clock."Also Read: Roger Federer brought to tears during his induction into International Tennis Hall of FameIt made for a lengthy first day of play, with Venus Williams and fellow wild card Sofia Kenin not getting on the court until past midnight - after their match was set to move to another stadium but the players decided to wait and keep it in the main venue.Nearly 12 hours earlier, third-seeded Jessica Pegula again experienced the benefits of the Sunday start that began last year."It is a little bit weird, but I did kind of enjoy that I could breathe for the next couple of days and everyone else is still freaking out about whether they're going to win their first round," she said.Djokovic later experienced the downside."We were just talking about it, and I said, it's so nice to play on Sunday when you win. But if you lose it's not nice, because you feel like the tournament didn't even start and you're out of it," No. 11 seed Marta Kostyuk said.Pegula and Kostyuk both won easily and now the get the benefit of any extra day of rest before returning for the second round, where Pegula would play either Williams or Kenin.Pegula leads the women's tour with 46 wins this season. She has two titles and has reached three other finals. Pegula can become No. 1 in the rankings if she wins her first major title and No. 2 Elena Rybakina loses before the semifinals.The No. 11-seeded Kostyuk beat Storm Hunter 6-4, 6-1 for a strong start to the year's final major after reaching the semifinals at the French Open and Wimbledon.A Sunday start but the champions don't begin until MondaySome of the biggest headliners don't begin until Monday. Two-time defending champion Aryna Sabalenka plays her opening match against Camila Osorio, before Carlos Alcaraz, who won his second US Open title last year, plays his first singles match since April after recovering from a right wrist injury.Past US Open champions Naomi Osaka, Iga Swiatek, Sloane Stephens and Stan Wawrinka are also on the Monday schedule, along with Wimbledon women's champion Linda Noskova and men's contenders such as Ben Shelton, Arthur Fils, Felix Auger-Aliassime and Frances Tiafoe.Daniil Medvedev, the 2021 US Open champion, shook off his miserable preparation for the tournament by beating Hugo Gaston 6-4, 6-2, 6-4. The No. 7 seed was just 1-3 in the North American hard-court swing, usually a time he thrives."Last couple of weeks was not easy," Medvedev said. "But I'm happy that today I managed to produce high-level tennis."Rain causes havoc, even in a stadium with a roofOther winners Sunday included No. 9 Elina Svitolina, No. 19 Jasmine Paolini and No. 31 Leylah Fernandez, the 2021 US Open runner-up. No. 27 seed Barbora Krejcikova, a two-time Grand Slam singles champion, lost 7-6 (4), 6-2 to Kamilla Rakhimova.American Tommy Paul, the No. 20 seed, bounced back from losing a first-set tiebreak to Coleman Wong to win 6-7 (3), 6-1, 6-3, 6-3. Wong a year ago became the first man from Hong Kong to win an Open-era Grand Slam men's singles match on the way to reaching the round of 32.Seven matches couldn't be completed because of rain - and one was delayed even though it was being played in the other stadium with a retractable roof. There was a mechanical issue with one of the sensors at Louis Armstrong Stadium, and even after the roof finally closed, the court had to be dried before No. 15 seed Alexander Bublik beat J.J. Wolf.Maric Cilic, the 2014 US Open champion, and 2022 runner-up Casper Ruud both withdrew with injuries.The US Open is in the process of getting a new lookThough the main draws didn't begin until Sunday, action at the US Open has already been going on for nearly a week. Large crowds gathered for the mixed doubles tournament, an exhibition headlined by Roger Federer's return to Flushing Meadows and the singles qualifying tournaments, with admission to the grounds free.Fans who came for the first time Sunday may have noticed a tournament in transition. The US Open is in the second year of a three-year renovation of Arthur Ashe Stadium, the main venue at the USTA Billie Jean King National Tennis Center. The improvements in the $800 million project include the addition of some lower-level seating, upgrades and additions of entertainment areas and the construction of a player performance center."Please pardon our appearance while we are reimagining spectacular," reads a sign above the entrance to Ashe.The project is scheduled to be completed in time for the 2027 US Open.