Following Kyrgios' latest controversy, the the 22-year-old blamed his retirement from the contest on a stomach bug. He was given a penalty for an audible obscenity during the tiebreaker, which he had also threatened to quit if he lost. "You are a joke".
"You look at that match today and you think "wow, you have got a long way to go" and it's not about the tennis - it's more about him as a person, his attitude and his ability to move on from hard moments in matches, " Croft added.
He was booed from the court by the crowd. "Is this normal?" Kyrgios asked somebody in the official area of the arena. "Emotions getting the better of him and he's off".
Combined, the fines totaled to more than USD31,000.
He wrote: "Guys I want to apologise to the fans in Shanghai and those that watched around the world on TV today".
'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've not eaten much the past 24 hours.
The tweet later appeared to have been deleted.
The ATP Tour said it had launched an investigation.
The director of the Brisbane International said Wednesday he would welcome Nick Kyrgios to his tournament with "genuine enthusiasm" even after the mercurial star stormed off court at the Shanghai Masters.
"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".
"What does that event mean?"
"But I think I served well, I had good concentration, had good energy as well, which I think is always important early on in a tournament". Big deal. I don't owe them anything.
"Exactly why I shouldn't come here".
"I just wanted to go out there today and kind of redeem myself a little bit from past year", he said, adding: "I just wanted to prove to myself how much I have improved".
He was then docked a point penalty for the second match running because of his conduct, which included belting a ball out of the court in a flash of rage.
Fellow American Jack Sock, the 14th seed, retired in his match because of dehydration with Ukrainian qualifier Alexandr Dolgopolov leading 4-6, 6-1, 2-1.