The Australian lost the first set in a tie-breaker before leaving the court.

Television footage and audio captured the 22-year-old telling his box he'd quit after a string of apparent bad calls, however, Kyrgios claimed he was injured and sick.

"Guys, I want to apologise to the fans in Shanghai and those that watched around the world on TV today," he said in a statement after walking off following a 7-5 first set loss against American Steve Johnson.

"I've been battling a stomach bug for 24 hours and I tried to be ready but I was really struggling on the court today which I think was pretty evident from the first point.

"My shoulder started to hurt in the practice today which didn't help either and once I lost the first set i was just not strong enough to continue because I have not eaten much in the past 24 hours.

"I'm hoping to be Okay for the doubles and will make a decision tomorrow morning, hopefully off a good night's sleep which I didn't get last night."

Kyrgios is hoping to remain in the tournament to play doubles, however, officials may not allow it.

Kyrgios was suspended a year ago after tanking at the same tournament.

"I'm gutted to be honest as I was keen to keep the good momentum that I built in Beijing going and finish the year strong," Kyrgios said.

"I'll do what I can to make sure I do."