Tom Humphries on the most recent metamorphosis of the Manchester City defender

There are a couple of ways of looking at Richard Dunne. The charitable view is the one taken by that kindest of men, Brian Kerr, when he asks why nobody looks at Richard Dunne and marvels at all that he has achieved by the age of 23.

And there's another way. You can flick quickly through his press cuttings and watch him evolve from Big Richard Dunne to Honey Monster Richard Dunne to the unfortunate Richard Dunne to soccer bad boy Richard Dunne to the reformed Richard Dunne. You can stop off on the good days, the matches after which he was hailed as a revelation, his time on Brian Kerr teams, his early Everton days, that Saturday night in Amsterdam, only serve to heighten the wonder: this is a man who had it all and almost wasted it all. A man who had it all and consumed it quickly.

There's a memory of him in Saipan before the war broke out. A quintessential moment one imagines in the life of the old Richard Dunne. 5:30 in the morning in the Beefeater Bar. Spring Onion-flavour Pringles all over the counter, drinks lined up in disorderly battalions, the air thick with smoke and songs and Dunne with something on his mind, buttonholing journalists to ask why they felt entitled to criticise his lifestyle. Not an ounce of irony.

He's changed now, although his face doesn't help convey that message. He always looks hangdog. Yesterday he sat in front of the media in the bowels of Lansdowne Road and he was lugubrious and worn as usual, but his body suggested the hard work he's been doing since his career almost came to an end last September when he turned up at Manchester City's training ground wearing the face and fragrance of a man who'd had a long, hard night. By then he was carrying two official warnings and Kevin Keegan felt entitled to make a criticism of his lifestyle. That came in the form of sending Dunne home, telling him not to come back for a week and meanwhile looking into the legal position as regards sacking him.

Famously, Dunne knuckled down. Like a man who has been to the edge, he began living life a little differently. As part of his rehabilitation, for six weeks he reported for training two hours early. Training at 8:30, again at noon and again in late afternoon. He submitted himself to a 24-hour fitness regime. Recently, in pursuance of club orders, he moved house from Southport outside Liverpool to Cheshire near Manchester. No more two-hour drives. No more mingling with the pals he learned to drink with as a kid at Everton.

The next good day in his scrapbook of cuttings would be the Manchester derby. Then he went to Greece for a friendly with Ireland and looked like the player he was once going to be.

At City since then he has been in and out. Tonight he starts for Ireland for the first time under the Kerr regime. Kerr hasn't included him in previous squads but he has no lack of confidence.

"He's played in some huge matches for his country and had some great games," the manager says. "He has a fair deal of experience. He has achieved a fair bit already. He has shown that in the heat of battle he can do his stuff."

At City he has been deployed everywhere and anywhere across the line of defence. Currently, as Keegan shuffles his formation, his business is right back. When you've had the clock winding down on your career, though, you don't quibble about what number jersey you wear.

"Right back is a way into the team," he says. "I want to play in the centre, but the more games I get the more experience I have. You have to learn. Every game you have to take something out of. "

There is a query about Keegan. Defence isn't his suit, really. It's hard to imagine that the old, glacially-paced Dunne appealed to him much. He must see something, because his forbearance has been remarkable and he can claim credit for rebuilding a fractured career.

"He's been great," confirms Dunne. "He stood by me through a lot of things. Last year I played more games than anyone at the club This year about 24 games. He asked me to change and I had to change. When I got back into the team my life had changed. It's been a whole new lifestyle. It seems to have done me good."

There have been times this season when he has looked out of his depth. He probably thinks of Dennis Bergkamp with much the same horror as Bergkamp thinks about flying. And he had a nightmarish 45 minutes against West Brom, of all people.

A long, settled run of first team football is what his career appears to cry out for right now. Perhaps tonight at Lansdowne would be a start.

The press conference winds up with a typical piece of Kerr theatre. He talks about a visit to the Viking museum at Roskilde, in Denmark.

"Lots of lovely stuff there," he says, and turns to the big man sitting to his left. "Stuff from Tallaght there, Richie. A whole section of stuff from Tallaght. They'd a boat there that was made in Dublin and a load of other stuff that was robbed here, but that wasn't the term they used. Of course, they had a big team back at that time."

The big man just grins. Old times. Kerr, the same old caffler, chief among the people rooting for him to put it right and be everything he can be.

There are two ways of looking at Richard Dunne. If at last he has decided to concentrate on his immense potential rather than his large appetites there might be a third way. Virtually a new player, an experienced 23-year-old centre half with a dozen years of football ahead of him. He's known many of those days that people describe as being the first day of the rest of their life. Today is another. Who knows what good times may lie ahead?