Novak Djokovic hit the wall as the 24-time Grand Slam winner vomited at the back of the court and was treated by the trainer during a disheartening first round loss which ended early Monday morning on opening day of the US Open.

The 39-year-old Serb fell ill – he said things have been this way for weeks – as he took a loss to Mariano Navone 7-6 (5), 5-7, 4-6, 6-2, 6-1.

In addition to his stomach problems, the ailing Serb was seen by the trainer, the doctor and used an inhaler as he complained of cramping and general poor health during a stress test lasting nearly four and three-quarter hours.

The defeat came a fortnight after Djokovic was knocked out in his opening match in Cincinnati after reaching a Wimbledon semi-final.

“It was obvious that it was an awful feeling on the court for me. It’s something I’ve been carrying, unfortunately, pretty much every match this year,” Djokovic said early Monday.

“Vomiting, throwing up, a serious issue there. Then my whole body starts to collapse, basically cramping and pain. 

“The back just gave up in the end and shoulder, and I couldn’t close it out.

He added: “I was up a break up in the fourth, but just struggled all the way since the fourth game of the match. Congrats to him. He’s a nice guy, a fighter.

But, you know, I didn’t enjoy myself.”

The disappointing end was Djokovic’s earliest Grand Slam exit in two decades and cut off a run of 78 Grand Slam first-round victories going back to a loss to Paul Goldstein at the 2006 Australian Open.

“From the perspective of the crowd and support, it was incredible, honestly from the beginning. They were trying to lift me up in important moments,” Djokovic said.

“I’m very sorry that I, you know, didn’t perform as well as I should have or could have… but the love and appreciation they gave me in the end really touched my heart.”

Seventh seed and 2021 champion Daniil Medvedev came good after losing here a year ago in the first round, posting a  win over Hugo Gaston 6-4, 6-2, 6-4 for his 33rd victory of the season.

Montreal quarter-finalist Daniel Merida defeated Marton Fucsovic 6-4, 6-4, 6-2 to earn the fist straight-set men’s win of the fortnight.

Jiri Lehecka put out two-time semi-finalist Pablo Carreño Busta 6-1, 7-6 (5), 4-6, 6-2. The win served as revenge after the veteran Spaniard beat the Czech in the Roland Garros first round.

No. 101 Dino Prizmic spent nearly four hours before completing a win over Alexander Shevchenko to advance in five sets.

The 2-6, 6-3, 6-3, 5-7, 7-5 success was hard-fought, with Prizmic leading 5-2 and serving for it in the fourth set but needing to go all the way to claim his first victory here after saving two match points.

The Croat has threatened top 10 names in the past, beating Novak Djokovic in Rome and Ben Shelton in Madrid.

Cincinnati quarter-finalist Tommy Paul recovered after losing the opening set, storming back for a 6-7 (3), 6-1, 6-3, 6-3 win over Hong Kong qualifier Coleman Wong.

Day 1 British results were mixed, with Cam Norrie going down in an upset loss to Frenchman Luca van Assche 6-7 (6), 6-2, 6-2, 6-3 while debutant Toby Samuel’s earned the biggest win of his career as he stunned Czech Tomas Machac 6-2, 6-3, 6-2.

Third seed Jessica Pegula got up and running on Sunday’s opening day at the US Open with an efficient   6-3, 6-2 defeat of Gabriella Ruse to reach the second round.

Pegula is in serious contention for a shot at the top ranking after earning a WTA-leading 46th match win of the season.

The American could become No. 1 by winning the title on the condition that rival Elena Rubakina does not go past the semi-finals next week.

She will wait for an opponent as wild card Venus Williams faces injury-plagued former Australian Open winner Sofia Kenin.

But the possibility of topping table is drawing little immediate interest from the seed with work to do here.

“I’d have to accomplish a lot of other really great things in order to get there. But I’m glad that it’s an option,” Pegula said.

“I think I’d have to win this tournament in order to be No. 1, but I think that just shows the level of women’s tennis right now and how well a lot of the top players are playing. 

“It’s definitely extra motivation, and I think it’s something that would be amazing, but again, it’s very, very, very, very far away.”

Pegula won with pair of breaks per set against Ruse. 

“I was so nervous today, always the first round of a slam,” the 32-year-old said after opening the programme on the Ashe showcourt.

“It’s an honour to hold that title, walking out onto Ashe opening day, first match, it’s amazing,” added the 2024 Open runner-up to Aryna Sabalenka.

With three-days of opening round play, Pegula now has two days off. “I get to sit around the site and watch everybody else freak out for the next two days,” she said.

Pegula, who was thrashed in last week’s Cincinnati Masters final by Coco Gauff, was joined as a winner by 13th seed Jasmine Paolini.

Paolini had to fight to hang onto a 4-1 lead in the last set, twice losing serve before breaking her opponent in the last game to pull off a move into the second round.

The Italian who did not play in Cincinnati due to a foot injury, defeated Slovene Veronika Erjavec 6-3, 3-6, 6-4.

The two-time Grand Slam finalist in 2024 said she was tentative at the start.

“It was a tough match my first on cement. I made a lot of errors, I was nervous and tense.

“But I’m pleased I was able to win and it can only help me in the next rounds. I had a lot of chances in he final set.

“Physically I’m doing better, but now I need to play matches.”

Former French Open champion Barbora Krejikova suffered a huge fall as she exited in the first round 7-6 (4), 6-2 to Uzbek Kamilla Rakhimova a year after reaching the quarter-finals here. The winner celebrated her 25th birthday by knocking out the first seeded player of the tournament.

Krejcikova, who lost in the first round at both tune-up events in Toronto and Cincinnati, lamented her poor summer form.

“The whole US tour didn’t go well for me. I’m just not in the best frame of mind,” the Czech said. “We’ve discussed it a lot internally, and it’s a combination of several factors. 

“The biggest one is probably that my batteries are flat. 

“It’s been plaguing me throughout the whole US tour. Although we’ve been preparing, training and working hard to improve, it hasn’t worked out in a single match.” 

Donna Vekic beat Australian Talia Gibson 6-2, 4-6, 6-3, with the winner dropping a double break in the final set but recovering to advance.

Australia suffered another early loss in 68 minutes as 11th seed Marta Kostyuk dismissed Storm Hunter 6-4, 6-1 in a bid for a third consecutive Grand Slam semi-final.

The Urkainian gave a post-victory shout-ot to her pair of dogs which travel with her and her husband on the circuit. 

2021 finalist Leylah Fernandez save five beak points in one game on her way to a 6-3, 6-2 start over Zhang Shuai.

Iga Swiatek has pulled out of the US Open mixed doubles mini-tournament this week in order to rest for the actual tennis, with the Cincinnati semi-finalist citing the need to rest.

The exhibition-style mixed, which has drawn serious criticism from actual doubles players, is limited to “celebrity” singles players, leaving only the chance for the top two doubles players on the men’s and women’s sides to try and qualify in a Monday shootout.

Swiatek has had a busy hardcourt month, winning in Canada before reaching the Cincy final four where she lost to Jessica Pegula.

She and Casper Ruud reached the mixed final in New York a year ago, which comprises only 16 teams, uses abbreviated scoring to speed things along and lasts a scant two days.

“Looking back at a physically demanding few weeks on court and after speaking to my team,,” the work No. 5 Pole said in a statement.

 “I’ve decided it’s best for me to pass on mixed doubles at the US Open this year. Right now, I need a few days to rest, recharge and fully focus on preparing for the singles tournament.” 

Swiatek joined Daniil Medvedev in giving the hit-and-giggle sessions a miss prior to the start of the final major of the season and is playing the tuneup 250 event in North Carolina.