NEW YORK -- If the last-name chorus of "Ruuuuuune!'' in support of his relatively unknown teenage opponent at the US Open bothered Novak Djokovic, he never let anyone know.
Nor was there any visible evidence that Djokovic was shaken by the shaky patches he went through while dropping a set Tuesday night as he began his historic bid to complete the first calendar-year Grand Slam in men's tennis since 1969 and collect a record-breaking 21st major singles championship.
Djokovic was not perfect -- "It wasn't the best of my performances,'' he acknowledged -- but he didn't need to be. All he needed to do was win, and he did, just as he has done every time he has played a Grand Slam match this season, whether on the hard courts of the Australian Open, the red clay of the French Open, the grass of Wimbledon or, now, the first of what he hopes will be seven times on the hard courts of Flushing Meadows.
Quickly regaining control after a second-set blip, then wearing down his cramping foe, Djokovic beat Danish qualifier Holger Rune 6-1, 6-7 (5), 6-2, 6-1 to reach the second round.
"I mean, obviously you always wish to have crowd behind you, but it's not always possible. That's all I can say. I mean, I don't know; I've been focusing on myself and what I need to do,'' said Djokovic, who next faces Tallon Griekspoor, a 25-year-old from Netherlands ranked 121st who got into the field when Roger Federer pulled out. "I guess I have to just see how it feels on the court and try to keep it together. That's all I can do."
So many differences between the two players in Arthur Ashe Stadium on a muggy Tuesday evening.
Djokovic is 34; Rune 18. Djokovic is ranked No. 1; Rune 145th. Djokovic owns 20 Grand Slam titles, the men's mark he currently shares with rivals Federer and Rafael Nadal; Rune, the junior champion at Roland Garros two years ago, had never played a match in the main draw of a major tournament until Tuesday. Djokovic's on-court career earnings entering this week were more than $150 million; Rune's were less than $150,000.
Rune showed up with some belongings in a blue Ikea shopping tote -- "It's a nice bag,'' he explained -- and wearing a backward-turned yellow hat, which he exchanged for a blue one after the first set. His descriptions of this match sounded as if they arrived from someone very much his age: All in all, he found it to be a "crazy experience'' and "a dream come true," and the crowd support was "unbelievable" and a "pretty sick feeling."
Rune did come in on a 13-match winning streak, built on the lower-level ATP Challenger Tour and the qualifying rounds in New York. The fans -- back at the US Open after all spectators were banned last year because of the coronavirus pandemic -- gave him some serious backing, responding to his pumped fists and uppercuts and pleas for more noise when he was playing at his best level in the second set.
What initially sounded like booing to both players was actually "Rune-ing," and the kid clearly loved the moment. So did his mother, clapping and smiling in his guest box, which also included Patrick Mouratoglou, Serena Williams' coach. Rune has trained at Mouratoglou's tennis academy in France.
Williams came so close to going 4-for-4 at the majors in 2015, before losing in the semifinals at the US Open against Roberta Vinci in one of the biggest upsets in tennis history. Had Djokovic lost this, it would have been even more of a stunner.
This year, for the first time, every match on every court these two weeks is operating without any line judges. Instead, the only human officiating is the chair umpire, while every shot is ruled in or out by a system that uses cameras to detect where balls land.
Last year, the US Open first tried relying on solely electronic calls for each match except those played at the biggest two arenas, Ashe and Louis Armstrong Stadium, where people made the rulings. It was during a fourth-round match in Ashe against Pablo Carreno Busta that Djokovic was defaulted after dropping a game in the first set when he smacked a ball that inadvertently hit a line judge in the throat.
Carreno Busta, who eventually made the semifinals in New York for the second time and then beat Djokovic for the bronze medal at the Tokyo Olympics this August, was a surprise first-round loser Tuesday. He was eliminated 5-7, 4-6, 6-1, 6-4, 7-6 (7) by Maxime Cressy, a Paris-born American ranked 151st.
Cressy played college tennis at UCLA, as did Mackie McDonald, the American who defeated No. 27 seed David Goffin in straight sets.
In other action, the two Olympic tennis singles gold medalists won: Germany's Alexander Zverev extended his winning streak to 12 matches with a 6-4, 7-5, 6-2 victory over Sam Querrey.
"I hope I can keep the level up and maybe even play better," said Zverev, the runner-up at the US Open last year, "because to beat Novak here is going to be an extremely difficult task.''
Reilly Opelka, the No. 22-seeded man, swept past Soon Woo Kwon, and fellow American Mackenzie McDonald upset No. 27 seed David Goffin 6-2, 7-5, 6-3. But Sebastian Korda, another promising young American, was eliminated when he retired against Nikoloz Basilashvili early in the second set.
Karen Khachanov, the No. 25 seed, was knocked off by Lloyd Harris 6-4, 1-6, 4-6, 6-3, 6-2.
American Jenson Brooksby moved into the second round by beating Mikael Ymer 7-5, 6-2, 5-7, 6-3. Brooksby was given a wild card into the tournament, though with his strong play this summer he has surged into the top 100 and would qualify automatically as of now. He reached the finals in Newport and the semifinals in Washington during the lead-up to the US Open. Another 20-year-old, 13th-seeded Jannik Sinner of Italy, beat Australian Max Purcell 6-4, 6-2, 4-6, 6-2.
American Taylor Fritz eliminated 14th-seeded Alex De Minaur in four sets to give the host country 13 men in the second round. That's the most players from the U.S. to win at least one match in the men's singles draw at Flushing Meadows since 15 did it in 1994.
Fritz won a three-hour match that ended just past midnight at Louis Armstrong Stadium by a score of 7-6 (4), 6-2, 1-6, 6-4. Both players won the same number of points, 127.
Fritz had lost all four previous matches he had played against Australia's De Minaur, who was a quarterfinalist at Flushing Meadows a year ago. The 23-year-old Fritz will now face a fellow Californian in the second round when he meets Brooksby. Fritz is ranked 42nd; Brooksby is 99th.
The Associated Press contributed to this report.