He was unaware of the US Open rule about time allowed between points. He barked in the direction of his entourage, among the only people in the Arthur Ashe Stadium seats. In the end, though, he did what he always does in 2020: win.
"I lost my focus," Djokovic said afterward.
"Kind of got stressed out a couple times. Screamed."
The No. 1-ranked Djokovic began his bid for Grand Slam title No. 18 on Monday night by extending his season start to 24-0 with a 6-1, 6-4, 6-1 victory over Damir Dzumhur at Flushing Meadows.
"Do I want to keep the streak going? Of course, I do. Am I thinking about it as a priority No. 1 every single day? No," said Djokovic, who opened 2011 with a 41-0 mark.
"I felt good on the court today," said Djokovic, who trails only Roger Federer, with 20, and Rafael Nadal, with 19, in the men's Grand Slam trophy standings.
Neither of those rivals is entered in the U.S. Open, only part of the reason Djokovic is an overwhelming favourite to win what would be his sixth title in a span of eight major tournaments.
One minor hiccup during his opening match had to do with the way the serve clock is being implemented at the U.S. Open: Chair umpires are starting that 25-second countdown much sooner now than they were during the Western & Southern Open.
Djokovic was not the only player to wonder aloud about that system during a match Monday.
"Why did you start it?" he asked chair umpire Damien Dumusois, noting that during the previous event players got more time to go collect their towels between points.
Dumusois said the pace is intentionally supposed to be quicker at the US Open, to which Djokovic replied: "You do it here different? Why? There is no explanation? ... Thanks for letting us know."
Alison Riske notched her sixth consecutive win against Germany’s Tatjana Maria on Monday night—prevailing, 6-3, 6-2, in the first round of the 2020 US Open. The 13th-seeded American was a force from start to finish, popping 36 winners, breaking serve five times on eight opportunities and winning 22 of 29 points at the net.
Returning to the court upon which she captured her first Grand Slam title in 2018, No. 4 seed Naomi Osaka survived an all-Japanese showdown with Misaki Doi, winning, 6-2, 5-7, 6-2, on opening night.
Gauff stunned in silence
Coco Gauff won over New York and became an instant fan favourite during her run of inspired tennis a year ago at the US Open. A year later, no fans, no energy, and no singles victory for Gauff - the teen sensation is out of the U.S. Open on Day 1. Anastasija Sevastova knocked off the 16-year-old Gauff in three sets, 6-3, 5-7, 6-4.
Anhelina Kalinina was in a quandary. Should the 145th-ranked Ukrainian make the long trip to New York for the U.S. Open not knowing whether she'd be in the field? She took a chance that paid off, even though she lost in the first round. Kalinina was on court for only 62 minutes during a 6-4, 6-0 loss to top-seeded Karolina Pliskova on Monday morning. She set off for New York needing help reaching the field - she was fifth in line for a slot - but moved in when other players dropped out.