SHANGHAI (Reuters) - Australian Nick Kyrgios caused more on-court controversy in his defeat by unseeded German Mischa Zverev at the Shanghai Masters on Wednesday with a listless performance that could land him in trouble with the ATP.
Zverev, 29, took just 48 minutes to beat number 12 seed Kyrgios, who had appeared uninterested throughout the second-round clash, putting in a series of half-hearted serves and barely moving to meet his opponent's returns.
The Australian also clashed with spectators before being booed off the court after losing 6-3 6-1.
At one point, Kyrgios, who reached a career-high 14th in the world on Sunday after winning the Japan Open, appeared to be walking off court before Zverev had returned a ball to him.
Kyrgios, later apologized on his Twitter account.
"Not good enough today on many levels, I'm better than that. I can go on about excuses but there are none. Sorry," wrote Kyrgios, who had also courted controversy during his opening-round win against American Sam Querrey on Tuesday, when he had said he was bored.
During his match with Zverev, Kyrgios became embroiled in an angry exchange with a fan who told him to "respect the game" and "respect the people".
The world number 12 replied: "You want to come here and play? Sit down and shut up and watch."
Kyrgios told a news conference afterwards that he did not owe spectators anything.
"It's my choice," he said. "If you don't like it, I didn't ask you to come and watch. Just leave.
"If you're so good at giving advice and so good at tennis, why aren't you as good as me? Why aren't you on the tour?
"You want to buy a ticket? Come watch me. You know I'm unpredictable. It's your choice. I don't owe you anything."
Kyrgios, 21, whose three ATP titles were all won this season, said he had been too "physically tired" to compete and had thrown in the towel.
"It was just tough," he told reporters. "Obviously I played a lot of matches in a row. Physically tired, mentally tired. That's why I'm trying to work on being able to be consistent every week.
Kyrgios has made as many headlines for his off-court antics as for his exciting tennis during his brief, but turbulent, career.
He pulled out of the 2016 Rio Olympics after a public spat with the Australian chef de mission Kitty Chiller, who said some of Kyrgios's social media posts suggested "he doesn't really understand what it means to be an Australian Olympian".
And at Wimbledon this year, Kyrgios was involved in a heated row in his post-match news conference after being challenged about his behavior and language, which earned him yet another code violation during his second-round victory over Dustin Brown.
His attitude was also questioned after he capitulated in his subsequent match against Andy Murray, rushing between serves and appearing at times to throw in the towel.
Reporting by Ian Rodricks in Bengaluru; editing by Ken Ferris, Neville Dalton