The 29-year-old Australian said a lingering abdominal strain plagued his serve in a 7-6 (7-3) 6-3 7-6 (7-2) first-round loss to young Scot Jacob Fearnley on Monday night.
Kyrgios said he was "heartbroken" at being unable to perform at his show-stopping best for the John Cain Arena crowd in the at-times ill-tempered affair.
"Realistically, I can't really see myself probably playing singles again here," he said after spending two hours and 19 minutes on court.
"I kind of was taking everything in tonight ... I didn't want to just throw in the towel and walk off or retire."
Kyrgios looked well below his best before a third set comeback, which proved not enough. (James Ross/AAP PHOTOS)
He credited the world No.86, although branded him "a f**king challenger player" on court when complaining about his own inability to generate pace on serve.
"I knew that I wasn't 100 per cent going into this match," Kyrgios said.
"I'm not saying that's why I lost. He outplayed me. He outserved me, he returned well, he did a lot of things amazing ... he's an in-form player."
It was Kyrgios' first appearance at a major since making the 2022 US Open quarter-finals and then requiring wrist and knee surgeries.
The 2022 Wimbledon runner-up, who still plans to play doubles with buddy Thanasi Kokkinakis, said he didn't expect to make it back to grand slam level.
"All the niggles, I guess, my body compensating with the wrist is tough," he said.
"It's just not enjoyable for me ... I'm happy to play through a bit of discomfort.
"But when it gets to a point where I'm one of the biggest servers on tour and I'm getting outserved tonight - my average serve speed was beneath 200km/h - Nick Kyrgios without his serve ... I'm not a threat to many players."
Ever the showman 🎪 the ol' underarm, behind-the-back combo 😂— #AusOpen (@AustralianOpen) Welcome back to the court @NickKyrgios!#CanadianClubAO • #Cheeky • #DrinkResponsibly • @espn • @eurosport • @wwos • @wowowtennis pic.twitter.com/juRvcUdU7NJanuary 13, 2025
He said he had no regrets over the course of his career and was aiming to play the remaining slams this year courtesy of his protected ranking, as well as doubles for Australia at the Davis Cup.
"I don't have any regrets. Everything's been a learning curve for me," Kyrgios said.
"I continue to to try and have fun and just be real and enjoy the ride.
"But I think it would be selfish for me to say that 'I want more, I want more'. I've had a lot of success. More than most athletes would have."
Playing on a protected ranking of No.21, Kyrgios still managed to force the opening set to a tiebreaker but fell behind in the count 6-1 and it proved unassailable.
The typically boisterous crowd in John Cain Arena tried to rally the former world No.13 after he dropped serve to go down 2-0 in the second set.
He went searching for answers from his box before calling for trainers, citing his abdominal strain as the issue.
"I had a grade one before I got here," he said. "I don't even know why I played.
"So f**ing dumb."
Fearnley played a calm and controlled match to dispose of Kyrgios in two hours and 19 minutes. (James Ross/AAP PHOTOS)
There were signs of life at 2-3 in the third set when Kyrgios bravely fought on to break after four deuces and get back level, then held serve to love to lead 4-3 after a stunning behind-the-back shot.
With the crowd sensing the moment, Kyrgios had a set point at 4-5 but again the Scot served his way out of trouble and won out in the tiebreaker.
Fearnley admitting to battling nerves ahead of the "rowdy" match and said he could tell Kyrgios was struggling.
"I could tell he was dealing with some stuff but I thought it was a great match," he said in his on-court interview.
Frenchman Arthur Cazaux, who upset 28th-seeded Argentine Sebastian Baez in a five-set epic, awaits Fearnley in the second round.
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