When Ireland played Australia in Dublin in 1991, the dashing scrumhalf Rob Saunders was filmed repeatedly punching himself in order to acclimatise his body to what lay ahead. This was in Lansdowne Road and the occasion was the World Cup rugby quarter-final, in which the Aussies were expected to waltz home.

Instead, the Irish responded to the occasion and conjured something they weren't renowned for back then: they moved the ball smoothly and scored a brilliant try. In that famous film clip you notice the surge of noise as the Irish moved the ball daringly and unexpectedly across the pitch from Saunders at the base of the scrum to allow Jack Clarke to outwit no less than David Campese before he sent Gordon Hamilton galloping clear for a brilliant try.

Ireland were exultant. The Aussies looked stunned – there was just four minutes left and they trailed 18-15. Hamilton sat with his arm raised and a huge grin across his face. It was a great try and his golden moment.

“Big Gordy’”was a flanker from Belfast. When you see that try now, you notice that by today’s standards, Gordy is built more like a rather slender inside centre than a flanker. And what you also notice is how much space there seems to be on the field.

When Ireland played South Africa in the Aviva recently, the dashing fullback Rob Kearney took a ball on the run, half-broke through a tackle and for a few thrilling seconds got to do what he does brilliantly: run with the ball in hand, making it up as he went. Then, he was engulfed by the monstrously bulked-up South African players.

First time

The first time I saw Kearney playing rugby he was a centre for Clongowes and he ran everything that that afternoon in Donnybrook. Now, at the peak of his career, he comes up against teams who are so physically imposing and against defences so well-spaced and drilled that they seem impossible to break through.

Even on television, you could hear the instant surge of anticipation in the crowd when Kearney bolted: it was a rare departure from the synchronised and patient pattern of methodical advance, of recycling the ball, of kicking for position, of setting the scrum, of the clipped instructions from the referee, of the rules at the breakdown.

The Kearney play seemed to shine a light on the general direction in which rugby is travelling and travelling at speed.

In Conversations with My Father, a book he recently produced with his daughter Justine, the former Ireland and Lions outhalf Jack Kyle observed: "The rules have changed completely as well, it is more of a kicking game now and the defences are so well organised that it has become much less of a running game, which I think is a shame. In our day, the ball came out of the scrum more quickly; nowadays it can be held up. Today, by the time the outhalf gets the ball, the other team is lined up waiting. The days when the likes of Cliff Morgan, Barry John and Mike Gibson could cut through the defence are very few and far between."

You can dismiss this as the pining of a 1950s hero for the halcyon days but it’s a pertinent observation from a man who is always at the forefront of the conversation about the best Irish rugby player ever.

Organised rugby union is well over a century old. The professional era will soon reach its 20th birthday. Rugby has made a tremendous success of the great leap from amateurism but is it in danger of leaving something essential behind?

The surface transformation of the game has been stunning. On Friday night in Connacht, the home crowd welcomed Mils Muliaina, an All-Black centurion onto the field of play in the Sportsground.

It was another indicator of just how successful Irish rugby has become at selling the game as an entertainment as well as a sport. It appeals to the old brigade of hardcore rugby fans as well as the thousands who attend who regard rugby games as a terrific winter diversion: scarves and hot cider and newly discovered provincial loyalty.

The new rules and endless fussing over the scrum have created an entirely new vocabulary for analysts and fans alike and the culture of professionalism has led to an inevitable predictability in the way the stars speak and behave.

Big men

All serious rugby teams contain terrific athletes and insanely big men. The bean pole locks; the frontrow financiers with a taste for psychopathic confrontation; the carousing hard-men; the fat tightheads with the dancing feet, the Baudelaire-reading and chain-smoking French stars and the moody genius number tens of the amateur age have gradually been phased out by elite, model pro athletes with ice-like temperaments and savvy contracts. A deluge of statistics is available for boffins and casual fans alike.

Coaching has been revolutionised and Joe Schmidt and Michael Cheika, Ireland and Australia coaches today, have both played huge roles in the recent development of Irish rugby. On the surface, it is wonderful. But when you watch rugby now, you can't help but feel that the spark of creative genius – the chink of daylight necessary to create something beautiful and clean and swift – is in danger of being snuffed out.

Brilliant as the win against South Africa was, the first half was a bore. You could see it in the faces of the RTÉ analysts and hear it in the long periods of silence in the stadium. When Ireland played Australia in 1991, all the Irish fans wanted to see was the ball in the hands of Simon Geoghegan, the fabulously inventive winger who would have been a superstar had he played for any other serious rugby nation.

The Aussies trusted their superiority to manufacture a late try that day and so restored the game’s natural order.

For too long, the match was remembered as the day Ireland nearly beat Australia to reach a World Cup semi-final. When the teams meet for their latest contest, Ireland will be tipped in most quarters to do so. That is a wonderful advance. The power and tackling and organisation and commitment from both sides will be something to behold and the analysts will highlight the pressure points of the scrum and the intricacies of recycling and the ferocious hits.

But you have to hope at some point the crowd will be treated to at least a glimmer of what Jack Kyle was referring to . The running game, as exemplified by the Welsh sides of the 1970s, the French sides of always, by Geoghegan and Brian O’Driscoll, has always been rugby’s essential gift to sport. If that is extinguished, rugby will lose the best of itself.