YOU don’t become a bad journalist overnight. It took me 44 years. Admittedly, I started at a level that would have given a limbo dancer a slipped disc but I managed to sink such a low degree that my shirt tail was singed by the Earth’s core.

As the sports editor remarked as he handed me as a leaving gift the box of Heroes the work experience boy had left for the sub-editors, the trajectory of my career could be used as the blueprint for the downhill slalom at the Beijing Winter Olympics.

But one can become a bad sportsman overnight. The margins in the professional game are so slight that the fall from great to rotten is shorter than Ronnie Corbett standing in a deep ditch. In contrast, the level of professional sport is higher than William S Burroughs asking for H on Countdown.

One was reminded by this truism by the hooking of John Terry last week. The Chelsea captain was the best defender in the EPL last season and on some days he may still be. But not when his central midfield leaves him as exposed as a ham sandwich at a Bar Mitzvah. And not when Sergio Aguero makes him look as nimble as a Chieftain tank with a dodgy gearbox.

The trouble is that professional sport is so unforgiving that even a dip in standards leads to humiliation. Most brutally, it occurs when the once sublime boxer starts to be hit more often than a website offering free porn and a pie.

It can be shocking. One’s hero suddenly becomes as useful as the sports editor in a crisis. One looks on in horror at how the great has fallen, oblivious to the reality that he may only be a fraction of a second slower than he was last season or in the last bout.

This lack of comprehension by the observer is accentuated by the reality that most punters do not have a clue what it is like to play at the top level. There is an eternal cry at football matches when an infuriated fan bellows at a feckless pro: “I could do better than that.” No, he can’t. And certainly not in a replica strip that reveals more ugly flesh than the open day at the local abattoir.

This delusion by the fan leads people to challenge top athletes at their discipline. The next-door neighbour columnist once played badminton for a living but a guy at a gym apparently assumed he could beat her. She declined his offer of a game with the riposte that she had given up badminton after the Olympics. He continued to press. Did he believe the Olympic reference was only one of time, as in “I gave up five a sides. When? Oh it must have been after the referendum”? She was a soddin’ Olympian, you moron, she would tank you playing in a deep-sea diver’s suit and wielding a frying pan.

The same thought assails my senses when I see Andy Murray’s second serve described as weak by the guy sitting next to you on the train. I once faced it, almost unwittingly, on a court in Paris where I was lurking while he practised. It went past me so fast I thought it was a woman I had asked to dance. This serve is the one that the top players can feast on, that Roger Federer adopts a pose like a hawk seeing a dormouse with a limp. Yet my first intimation of its presence was a loud thump behind me.

The same is true at rugby. One of the most esteemed rugby writers in Scotland once trained with the Scotland squad and attempted a tackle. His shoulder still hurts. A decade on.

Similarly, I always took the chance to watch the pros train when I was on the football beat. The pace and the intensity was far beyond anything that could be appreciated from the distance of the stands. Yet this gap remains unseen by many spectators who assume that the pros are just a wee bit better, a wee bit faster, a wee bit stronger.

There is only one way to end this lack of perspective. That is, to allow the punter on to the field of play. In the 100 metres Olympic final, there should be a ninth lane where, say, a driver of the last train on the Northern Line Tube should compete against the other athletes. Then we would see how fast they were.

Or, more pertinently, every professional football team has to pick a guy out of the stands every Saturday. He has to be overweight, loud and have no dress sense. That leaves them about 40,000 to choose from on any given matchday. The non-pro would immediately make even that guy who played left-back for Motherwell last year look good.

He would also provide evidence that while John Terry and others may be slipping they remain out of sight for the mere mortal. The decline of powers is inevitable. Just ask the sports editor. Or, better, look at the reference he gave me.