Just three days after winning the Japan Open, the Australian player, who is known for fiery outbursts and argumentative behavior on court, put in little effort in the second-round match against Zverev, a player ranked 110th in the world who had only won seven ATP Tour matches all season.
Kyrgios tapped a soft serve over the net and started walking toward his chair before Zverev had even returned the ball. He floated other first serves in at 67 mph and smacked second-serve faults at 130 mph.
Kyrgios hit a risky trick volley between his legs -- and still managed to win the point. On changeovers, he bypassed his chair and waited impatiently to serve, twirling his racket on his fingers.
Chair umpire Ali Nili admonished Kyrgios for his behavior in the first set.
"This is a professional tournament, you have to act like a professional," Nili said.
Toward the end of the 48-minute match, the crowd started booing and jeering. One man yelled, "Respect the game," prompting a furious reaction from Kyrgios, who shouted, "You want to come here and play?"
Asked after the match whether he thought he owed the spectators a better effort as one of the stars of the game, Kyrgios turned defiant again.
"What does that even mean? I'm good at hitting a tennis ball at the net. Big deal. I don't owe them anything," he said. "If you don't like it, I didn't ask you to come watch. Just leave."
On his soft serves, he replied flatly, "My arm was a little sore."
Kyrgios conceded that he didn't put forth his best effort and was mentally drained after winning his third title of the season in Tokyo.
"I guess that's why I'm trying to work on being able to be consistent every week," Kyrgios said. "Just took the easy way out tonight and obviously didn't show up at all."
He added that he is so tired from the lengthy season, that he's not interested in chasing one of the last spots for the ATP finals next month.
"I couldn't care less, to be completely honest with you," he said.
Kyrgios later apologized on Twitter.
Zverev joked about some of Kyrgios' serves after the match -- it felt like the last time he played his girlfriend, he said -- but he also defended the Australian and said he shouldn't be criticized for his professionalism.
"Would Federer behave like that? Probably not," Zverev said. "But [Kyrgios] has a creative mind. ... He's top-15, -16 in the world, so he's doing something right."
Zverev also said it's normal to be fatigued at the end of a grueling season.
"You reach a point where you're mentally tired and some people react one way, some people react a different way," Zverev said. "It doesn't say anything about whether he's professional or not."
Defiant Kyrgios throws match
Nick Kyrgios gets into a spat with the crowd and shows little effort in his 6-3, 6-1 loss to Mischa Zverev at the Shanghai Masters.