The problem with cocaine is without exception it transforms the person who takes it into the most tremendous dickhead. If Conor McGregor is not lately around the clock shoving industrial quantities of the drug up his oft-broken nose – as increasingly fight fans believe he must be – then he might as well start to. No one would notice. Since losing what was in hindsight a ludicrous boxing match to Floyd Mayweather in 2017 and then a year later being brutalized in a cage-fight by walking hairline Khabib Nurmagomedov, McGregor’s behavior has become boorish in the extreme. The disarming bursts of wit and charm that previously made the worst excesses of his foul-mouthed braggadocio tolerable have evaporated. What’s left seems fast to be becoming the fight game’s greatest cliché – a raging bull embittered by his inability to any longer achieve the self-discipline that propelled him to glory, or the commitment to a craft that, crucially, surpassed his love of lucre.

The latest incident, in which McGregor was filmed punching an apparently blameless septuagenarian in the face in a Dublin bar, seems very much in keeping with the recent rapid downward trajectory of his behavior. If McGregor is not careful, before he knows it his transformation into a laughing stock will be complete, and that would be a tragic way for a once inspirational young man to finish his fighting career, never mind how much money he has in the bank.

It’s not hard to understand what has happened to McGregor, which doesn’t make it any less sad. On the way up, when no one seemed able to beat him in combat and his every wise-crack was cheered to the echo (by people like me), he was encouraged, even incentivized, by his masters to indulge his natural enthusiasm for the outrageous. As part of the promotion for the Mayweather fight, for example, he was required to travel around America and to London in order to appear on stages in front of tens of thousands of ecstatic fans in vast arenas and volubly to insult his opponent in the most lurid way possible. The entertainment was base, certainly, but how thrilling it must have been for this former plumber from Dublin, a natural extrovert, to commune with his fans in this manner and to experience first-hand, for hours at a time, the kind of wild adulation usually reserved only for rock stars. Already famous, in the build up to the Mayweather fight McGregor became a global icon, no matter that in the actual bout he was hopelessly outclassed. Sure, he was paid an unimaginably vast sum for taking part in the contest but when the bell sounded his trash talking was quickly exposed for the hollow idiocy it was. As the world watched, he was thrashed.

The same pattern – the brazen throwing of outlandish insults about his opponent followed abruptly by overwhelming defeat – was repeated in the build up to the fight against Nurmagomedov. Again, McGregor received a hefty purse, but the disparity, impossible to ignore, between what he said would happen (‘I’ll stamp on his head until he’s unconscious’) versus what actually transpired (surrender in round four while being throttled) made the Irishman appear foolish. Both fights enriched him massively, but for each he paid a terrible price in the only commodity that really matters to a fighter, which is pride.

Look at him now. Every few weeks some new, always tawdry, complication. Arrests for offenses ranging from speeding to criminal mischief to disorderly conduct (the latter for throwing a metal trolley through the window of a bus carrying Nurmagomedov). Allegations – all denied – of extramarital affairs, a lovechild, even rape. Apparent death threats from murky Irish underworld figures. Photos in which he is obviously intoxicated and footage of him haranguing the referee during a bizarre intervention in which he entered the cage during a friend’s fight. Suddenly the once megawatt bombast no longer carries all before it, while the still frequent boasts of greatness hold no weight. How can they when recent record consists is two wallopings?

How wonderful it would be if McGregor could turn it all around. At his best, he would still be the most exciting fighter in the world. He claims to live to fight, but surely with £200 million in the bank and a fleet of high specification Rolls Royces in the garage it’s impossible to retain the requisite hunger. The flesh is willing, maybe, but the heart not so much. Would McGregor return every penny of the money he earned for fighting Mayweather and Nurmagomedov if it meant the outcomes were reversed? That’s a question only he can answer, but certainly his actions since the losses have not seemed those of a man at ease within himself.

McGregor’s likable long-time fighting coach and mentor John Kavanagh has spoken since the Nurmagomedov fight of becoming estranged from his star pupil. Asked in numerous interviews about what McGregor will do next, Kavanagh now seems to wince a little before speaking obliquely and wistfully of a desire for McGregor to return to being the man he once was. ‘I hope we return to doing positive things again,’ he told one interviewer. To another, he borrowed an analogy from the famous Rocky films about a fighter who rises from nothing to conquer the world before losing his way and becoming bloated by success: ‘We had this up-and-coming guy, and I want to go back and get the eye of the tiger. Go back to this old school gym and just kind of disappear,’ he said. Could it happen?

In the summer, cage-fighting’s leading commentator Joe Rogan was asked what he thought McGregor would do now. He responded immediately: ‘Whatever he wants. Probably a lot of coke.’ He added he was joking, but the statement struck a chord with those who worry McGregor has started out down a well-worn path that leads to a dark place.

At the end of last year McGregor spent £3 million on a yacht and named it 188. The gesture was intended as a reminder of where he came from – 188 being the number of euros he received each week while on the dole in Ireland. Clearly, he’s come a long way since those days when he seemed high on nothing more harmful than craic. It’s hard not to watch documentary footage of his rise without forming the conclusion that the version of the man he was when he didn’t have it all was not only easier to like, but happier, too.