WHAT'S good for the goose is good for the gander, or in this case perhaps, the other way around. The wave of bright young managers instigating a mini tactical revolution in the English game ought to be of immense benefit to a kindred spirit taking charge of his first game as Republic of Ireland manager tomorrow night.

Mick McCarthy is wasting no time in experimenting with a new system against what promises to be a fluid Russian outfit at Lansdowne Road, comforted as he is by the knowledge that more and more of his players have become used to such a formation at club level.

"I've a few teams in my mind, but I know what the team will be if everybody turns up. I'll play with three centre backs, two full backs pushed on, three in midfield and two up front," McCarthy revealed yesterday in the squad's base at the Trust House Forte hotel after a private training session. "And if I can slip another one in somewhere and get away with it I will," he quipped.

At times in recent Republic of Ireland games, it's seemed that the green shirts were indeed outnumbered, primarily in central midfield. Hence, an equally important factor in this variant of 3-5-2 towards countering the hitherto more numerous midfield base of the continentals is a three man central midfield.

Not many teams play with wingers anymore, as such, particularly European teams," explained McCarthy. "The full-backs are more often than not stuck out there not doing a great deal. When you play 4-4-2 you get passed around all the time, as was proved against the Dutch and Portuguese."

Echoing Jack Charlton in his earlier use of John Aldridge, McCarthy also added: "Perhaps there's lessons for the two front men to be learned in terms of one of them dropping back into midfield and helping out in there."

When deprived of Niall Quinn in 1994, Charlton officially pronounced his system 4-5-1. It was more successful than is generally acknowledged in the run up to US 94 and, in moderately favourable climate, against Italy and Norway. Critics would point to the 3-1 defeat in Vienna, when Charlton reverted to it with Quinn as an ill fitting and reluctant lone striker, but again the stronger central midfield base enabled the Irish to dominate long stretches of that game.

In any event, times have changed greatly since Charlton took charge initially, when good old 4-4-2 was carved in stone and passed on from generation to generation in tablet form. English managers have repeatedly bemoaned the comparative tactical inflexibility of their players compared to the continentals, but the straitjacket is slowly being unbuckled by the likes of Brian Little, Roy Evans and Glenn Hoddle. McCarthy admits "it does help".

"I think in the past, certainly when Jack Charlton first took over, all the English teams played 4-4-2 and it was very rigid, very basic 4-4-2; two wingers up and down wide, two midfield players, the wingers tuck in when they lose the ball. It's changed. The way of playing has changed."

As regards 3-5-2, Aston Villa are doing it, and, as we saw on Sunday, to telling effect. Likewise, it's the established system at Liverpool and Chelsea, with considerably more success than at the recent converts, Leeds. Viewed in that light, the withdrawal of a fatigued Gary Kelly yesterday due to a knee injury may not be such a bad thing, given his own misgivings about adapting to a wing back role at Leeds from his customary full back portfolio in 4-4-2.

Kelly thus joins Alan Kelly, Dennis Irwin, Phil Babb, John Sheridan, Alan McLoughlin and Ray Houghton on the enforced absentee list from the original 23 man squad.

Despite the unavailability of Babb, who increasingly seems to be one of the prime beneficiaries of Evans' system at Liverpool, as many as four of McCarthy's "back five" of centre halves and wing backs operating tomorrow night could he plucked from the same system at club level.

Jason McAteer has nailed down the right wing back role at Liverpool, where Rob Jones remains stationed on the left, while the Villa pair of Paul McGrath and Steve Staunton have experienced the system, thereby granting the former yet another lease of life. Furthermore, given a freer, touchline hugging left wing back's role at Chelsea, Terry Phelan looks altogether more comfortable than the de facto left sided midfielder who struggled in the Anfield play off.

Of course, Liam Daish (who joins the squad today after Coventry's game at Southampton last night) and Alan Kernaghan are further central defensive options, while McAteer might well be employed in midfield alongside Roy Keane and Andy Townsend, with Jeff Kenna on the right. Whatever, every little bit helps.

"I think you can certainly be a bit more fluid, especially with the three in midfield. But the three at the back have got to be able to pass it. There's no point in playing three centre backs and clattering it forward." Heresy in the JC years perhaps, but cue McGrath.

The notion that McCarthy might yet be able to wring another year out of the 36 year old maestro, as Little has done at Villa, is almost too good to be true. But the Danish sweeper Morten Olsen carried on until he was 40, with the likes of Franz Beckenbauer, Franco Baresi and co not far behind, while McGrath started a professional career comparatively late at 23.

"It would be nice if it could extend his international career by another year, wouldn't it? For him and for us. He could get away with it in a three man defence but I don't think he'd get away with it in a two man (central defence). He does read the game so well. If he plays in the middle of three he doesn't have to be going covering the full backs and chasing into the channels. He can play of course. He's good with the ball. Paul McGrath. He's a good footballer."

McCarthy has eight games with which to experiment before qualification for the 1998 World Cup finals in France begins away to Liechtenstein on August 31st, and the experimentation won't stop tomorrow.

Gradual changes in personnel will also be conducted. The numbers aren't there to do it any differently. But clearly McCarthy is not fazed by youth, and confirmed he was strongly considering granting the 19 year old Blackburn goalkeeper Shay Given, currently on loan to Sunderland, a debut.

McCarthy's more pressing concern is finding cover and options up front. Interestingly, he bemoaned the injury which has denied him Dave Kelly, and intimated that he might have retained faith in the unlucky Sunderland striker longer than Charlton did after the curtailed England game a year ago.

So it could be that the front runners will be Niall Quinn and John Aldridge, which has a familiar ring to it. Something old then, and something new, something borrowed and, in this case, something green.