The Irish trio prepare for crucial engagements in varying states of disrepair, none more so than Ulster. During the course of completing a 14th win from 15 unbeaten home matches in the Guinness PRO12, they lost more players in an hour than most teams lose in a month.
Overcoming Edinburgh turned out to be anything but routine for Ulster. They endured so many cruel blows that theirs appeared to be a severe example of a pyrrhic victory - one achieved at too high a cost.
Where that leaves them against Toulouse in Belfast on Friday evening remains to be seen. For a start, it leaves them without four players - Iain Henderson (torn hamstring), Darren Cave (damaged shoulder), Dan Tuohy (broken ankle) and Peter Nelson, out for the season because of a dislocated foot.
Ulster's home setback against Saracens in the previous round will serve to heighten Toulouse's sense of wariness over their reappearance at a familiar venue. No student of the European scene needs to be told that they lost twice on successive visits to Belfast in rapid succession during Ulster's march towards their famous victory in the 1999 final, achieved at the expense of a club from the outskirts of Toulouse, Colomiers.
Toulouse laid some of those ghosts to rest with a narrow win at Ravenhill two seasons later. They probably wished they hadn't, judging by what happened on their subsequent appearance in Belfast, for the opening pool round of the tournament in October 2006.
Ulster didn't so much romp home by a street as by the length of the Champs Elysees. By the time the music stopped that night, Toulouse found themselves 27 points behind, routed in what Ulster's then coach, Mark McCall, acclaimed as a 'brilliant performance.'
Andrew Trimble, who had turned 22 the day before, stole the show with a try inside two minutes followed by another before half-time. He is one of three survivors from the starting XV of nine years ago, along with Rory Best and Roger Wilson.
Toulouse, whose team way back then included Ireland's Trevor Brennan in the second row, have not been back north of the Irish border since. Having lost at Saracens in very trying circumstances the day after the Paris massacres last month, they dare not slip again if they are to have a realistic chance of qualifying for the last eight.
The same, of course, goes for Ulster. A host of French clubs have lost there, not just Toulouse but Clermont Auvergne, Montpellier, Castres and, most frequently of all, Stade Francais - beaten in five visits out of six.
English challengers tend to be given even shorter shrift at Thomond Park than the French in Belfast. Munster, five points out of five thanks to making the most of their pool opener against Treviso, must extend that run of home invincibility against opponents as familiar as they are formidable.
Leicester Tigers are still the only English club to have won a European tie in Limerick. While their solitary success in January 2007 stands out as an example of one win being once too often from a Munster perspective, twice would be unthinkable.
Leicester come armed with ten points out of ten and one defeat in eight matches all season. Munster may still be within striking distance of the top of the Guinness PRO12 but there's no escaping the fact that they have lost their last two matches - to Connacht and the Dragons.
A number of big hitters - BJ Botha, CJ Stander, Keith Earls, Francis Saili, Donnacha Ryan, Ian Keatley - were missing at Rodney Parade last Sunday but that in no way detracts from a famous win for the Welsh region on a weekend when all four came up trumps.
The Blues stopped Connacht's winning streak, clearing the way for the Scarlets to topple them from their perch against Treviso the day before the Ospreys marked their Italian trip by taking all five points at Zebre's expense.
The Dragons reacted to all that with a victory over record-breaking dimension. Their 22-6 beating of Munster topped the previous best of 20-6 at the same venue four years ago.
The result sent Munster home in sombre mood. ''We want to get our heads down now,'' head coach Anthony Foley said. ''And make sure we get a performance against Leicester to stop this rot.''
When the Tigers found the nerve to win at Thomond Park, in the last round of the 2006-7 pool competition, they did so with a strong Irish flavour including an Ulsterman at fly half in Ian Humphreys.
Geordan Murphy scored one of his team's two tries in a 13-6 win, aided and abetted by a pair of exiled Leinstermen in the pack - Shane Jennings and Leo Cullen.
At Twickenham a few months later, the pair celebrated their first European title before returning home to win three more with Leinster. Cullen, captain in all three, knows that another defeat on top of those inflicted by Wasps and Bath will leave the former triple champions down and out.
All they have to do beside the Mediterranean on Sunday afternoon is win where no opposing team has won before, at the Stade Mayol. Toulon have swept all before them there in the course of their European Cup hat-trick and now they will be further reinforced by the All Blacks' centre, Ma'a Nonu.
The deluge brought by Storm Desmond at least allowed Cullen and his coaches to concentrate on the Toulon mission without running the sort of injury risk which bedevilled Ulster. The flood which washed out their Guinness PRO12 fixture at Scotstoun put the Warriors in the same boat in terms of preparing for their Champions' Cup tie in Glasgow on Saturday against the Scarlets - a must-win for both teams given the damage caused by home failures in the previous round.
Ospreys, their challenge for the last eight strengthened by their double bonus point as due reward for running Clermont close in the previous round, know they must make home advantage tell against Bordeaux-Begles in Swansea on Saturday.
Benetton Treviso kick off an hour earlier, a home tie against Stade Francais presenting the Italian team with another challenging task. They have beaten French opposition before, most recently against Perpignan six years ago.
Some relevant results from yesteryear:
October 21, 2006:
Ulster 30 pts (Tries-A Trimble 2, I Boss. Cons-D Humphreys 3. Pens- D Humphreys 3). Toulouse 3 (Pen- V Courrent).
Ulster: B Cunningham; T Bowe, P Steinmetz, P Wallace, A Trimble; D Humphreys, I Boss; J Fitzpatrick, R Best, B Young; J Harrison, capt., M McCullough; N Best, S Ferris, R Wilson.
January 20, 2007:
Munster 6 pts (Pens- O'Gara 2). Leicester 13 (Tries-G Murphy, O Smith. Pen-I Humphreys).
Munster: S Payne; J Kelly, B Murphy, L Mafi, I Dowling; R O'Gara, P Stringer; M Horan, F Sheahan, J Hayes; D O'Callaghan, P O'Connell, capt.; M O'Driscoll, P Wallace, D Leamy.
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