Yet for their captain, this can be seen as the game that justifies a decision he estimates to have cost him a five-figure sum. It is some way short of big money in these semi-professional times but by his decision to opt out of international rugby for a season - and so concentrate on leading the Irish into the English First Division - it is Garry Halpin's personal sacrifice.
Halpin is not in the major league of well-heeled rugby identities, not as a teacher of geography at St George's College in Addlestown, Surrey, however respected his pedagogical skills may be. But yer man does not ultimately expect to have lost a penny - provided always that London Irish gain the second promotion place after Northampton. So for altruism read an Irish punter's eye for the main chance.
"By choosing to drop out of the Ireland set-up it's cost me maybe about pounds 12,000," he explained. "But put it this way: I would fully intend to make that money up next season. I make no bones about it. If we make the First Division, we have an agreement that I would be made up for this and that's been a big driving thing for me. Either way, I'll come out of this smiling."
This is no more than straight realism from a genuinely top-rate fellow. Halpin has speculated on his and London Irish's future in the hope - now expectation - of accumulating. If the Irish's semi-final has the corollary of showing Ireland what they have perforce been missing, so much the better for his prospects of being recalled next season.
A curious thing is that Halpin, 30 last month, should have stepped aside at the very moment he appeared at long last to have secured the place at tight-head prop which was first his in 1990 when he was playing back home in Dublin for the Wanderers club before crossing the water in 1991. He has since accumulated only 10 caps but as the last three of those were during the 1995 World Cup he approached this season favoured as the man in possession.
It made no difference. "When I see Ireland playing at Twickenham, of course I would love to be playing," he said. "But I never doubted I did the right thing, both for me and for the club. The first thing was I was tired after the World Cup - I just didn't have the ambition - and coupled with that there was the captaincy of London Irish."
In this regard the impressive presence of Clive Woodward, the former Leicester and England centre, as club coach had a powerful bearing. "I knew it was going to be a big and demanding job, and Clive does nothing half-heartedly: you do it totally committedly or you're no good to him. I very much agree with, and believe in, that philosophy.
"Because of this, everything was very clear for me. I could foresee too much hassle between London Irish and the Irish RFU about player-availability and I didn't want to be in the middle of that club-v-country thing, wondering what to do when the IRFU wanted to take me out of important games. If I, as captain, had to leave every time, it wouldn't work.
"I'm quite influential in our team. There are a lot of young guys who sort of look up to me, even if it's the first time in my life anyone's done that. So I was making a statement that I had given up international rugby and this was the level of commitment I was willing to make for the club. They responded."
The result is second place in the Second Division, two points behind Northampton (who have two games in hand) but more relevantly two ahead of London Scottish with four to play and a vastly superior points-difference. This is why next Saturday's visit to Wakefield is of greater significance to Halpin and his team even than today's showcase occasion.
It is also why the semi-final worries Halpin and Woodward so. On the one hand, players' minds have been so fixed on, and nerves so tight about, Leicester that training has been adversely affected. On the other players' minds are at the same time so fixed on the Wakefield match that the captain fears they may not do themselves justice today.
"If I had a choice, I would love to play this game after our league campaign. Its timing is appalling from a preparation point of view. We have what we know will be a very physical game this weekend and then have to go to Wakefield next weekend for another physical game. It bugs me that it's happened this way, that we can't hype this game as we should, and our mental preparation could be a lot better."
The crowd approaching 7,000 who will fill Sunbury may beg to differ about relative significances but in any case the semi-final should provide the exiles - and Woodward and Halpin in particular - with a yardstick of what to expect next season and how far they will need to go in strengthening a promotion-winning team.
To this end an influx of Irish and sundry non-UK players is expected once the First Division has been attained, so on second thoughts perhaps today's exercise will not be such a yardstick after all. Whatever, by next season Halpin hopes (against hope) that the club-v-country issue, which has bedevilled London Irish's relationship with the Irish union, will have been resolved. Then he will be ready to restake his claim.
"I know I've had a chequered international career but I was always very aggrieved at the people they picked ahead of me. In the ability to play rugby I'm as good as anybody there and, internationally, I still have huge goals. I've taken my year out, I'm recharged, and I want to go on the Lions tour to South Africa next year.
"I may not have that many caps but the only other tight head I would really regard in these islands is Darren Garforth and if I got a Lions tour, five or 50 caps for Ireland wouldn't matter a damn." The uncapped Garforth, as it happens, plays for Leicester against Halpin today, so you could say the Lions hunt starts here.Reuse content