It's been a frustrating few days for Nick Kyrgios, but when is he ever happy?The 22-year-old is too often talked about for the wrong reasons, and here we are again at the Shanghai Masters.Days after losing the China Open final to Rafael Nadal in straight sets, the Australian was looking to make amends with a good run in the tournament.His first task was to overcome Steve Johnson of the United States.Against Nadal, he had at least started promisingly but then lost his way after becoming frustrated at a line call.Now, he's failed to cover himself in glory again.Johnson is through to the second round, and he won't have had many easier victories in his career.That's because Kyrgios chose to retire after the first set - we say 'chose' quite deliberately, as he didn't appear to be injured.

More controversy for Kyrgios 

Umpire Fergus Murphy and Johnson both looked rather confused as to what had just happened, which is understandable as there isn't really a precedent for this kind of behaviour. Take a look at their responses:

If it's true that Kyrgios wasn't injured, it's quite possible that he'll face consequences for his actions from the authorities.

ATP journalist Enrico Maria Riva has attempted to shed some light on why exactly he walked off, but it doesn't make his actions any less bizarre:

Kyrgios was on the end of what he deemed a bad call and was then heard to swear at hecklers and hit two balls out of the stadium. Just another day in the life of the controversial star.

He wasn't happy 

It appears he was already in a bad mood even before the match had started. No great player likes losing, but when he's reacting badly to losing a coin toss, it's no wonder there are such question marks against his attitude.

You stay classy, Nick Kyrgios.

Should Kyrgios be punished for his actions? Have your say in the comments.