Heineken Cup champions Leinster face a massive battle in Sunday's semi-final in Bordeaux against a star-studded, in-form, Clermont side.
After a faultless tournament so far, Leinster are still on track to become only the second club (after Leicester) to win back-to-back titles but facing Clermont in France is the ultimate challenge in European rugby these days.
Les Jaunards can boast a 42-game unbeaten streak at their fortress in Clermont-Ferrand and although Bordeaux is a three-and-a-half-hour drive west, expect Stade Chaban-Delmas to be awash with yellow and blue jerseys and covered with the banners of the Ultras Vulcans supporters club.
As Saracens found out in the quarter-finals, when the Clermont fans find their voice - and they always do - the old cliché of the 16th man in the stands becomes a very real element to deal with.
Indeed the very fact that Leinster must travel to France is worthy of a raised eyebrow. Despite Clermont having lost to Ulster and Leicester in the pool stages while Leinster swept all before them, the luck of a nonsensical draw means that the Irish side will be the away team when it matters most.
But Joe Schmidt's side will not dwell on the matter. Leinster are unbeaten in their last 13 European matches and have been in devastating form recently having crushed Cardiff in their quarter-final, before beating both of the other semi-finalists - Edinburgh and Ulster - in the PRO12.
What's more, the Dubliners will have invaluable insight into how the Clermont side functions. Schmidt knows Clermont better than most having coached their back-line for three years, including their 2010 Top 14 title-winning campaign.
Perennial underachievers in Europe, Clermont have made claiming their first Heineken Cup crown their number one priority in their centenary season. And so far so good as they emerged top of arguably the toughest group in the competition and went on to outclass Sarries in the quarter-finals.
With inclement weather forecast, Clermont's display at Vicarage Road - where they didn't dominate possession but were immovable on defence, and executed clinically when opportunities presented themselves - will have Leinster worried. An arm-wrestle is not what the Irish side want, as a hallmark Vern Cotter's team is their patience and their ability maintain numbers in the defensive line without being sucked into rucks.
Clermont have made three changes to the starting XV that beat Montpellier last week as French internationals Julien Malzieu and Aurélien Rougerie return while veteran flank Julien Bonnaire comes in for the injured Gerhard Vosloo.
For Leinster, Gordon D'Arcy partners Brian O'Driscoll at centre with Luke Fitzgerald joining Isa Nacewa - who will make his 99th Leinster appearance - and Rob Kearney in the back three. Isaac Boss links up with Jonathan Sexton - who has scored 77 points to date in this year's competition - at half-back.
24-year-old prop Cian Healy, who makes his 94th Leinster career appearance and his 36th in Europe, starts in the front-row alongside Richardt Strauss and Mike Ross.
Leo Cullen leads the team and partners All Black Brad Thorn at lock, with Shane Jennings joining fellow Ireland internationals Sean O'Brien and the returning Jamie Heaslip in the back-row.
These teams have faced each other five times with Leinster the winners on four occasions but the fact that they last tasted Heineken Cup defeat when they went down 20-13 at Clermont last season will not be lost on Cullen and his team-mates.
Players to watch:
For Clermont: Having played a decisive role in Clermont's victory at Vicarage Road, Brock James went some way to wiping away the memories of his nightmare meltdown in the quarter-final against Leinster two seasons ago. He's been in cracking form since and with David Skrela out injured, the Australian will be called upon to steer the ASM attack again. He has a wide arsenal of kicking options that will provide plenty of opportunities for his line-out jumpers as well as balls to chase down for wings Sitiveni Sivivatu and Julien Malzieu. Georgian prop David Zirakashvili's work-rate is phenomenal but there have been suggestions in the Irish press that Leinster will target him at scrum time. With deadly place kickers on either side, how English referee Wayne Barnes interprets the set-piece showdown could provide the key to the result.
For Leinster: The one-and-only Brian O'Driscoll marked his return from injury in classic style against the Blues, and Leinster will look to their favourite son to spearhead their attack. BOD now lies just a single try behind Vincent Clerc's record of 32 in the competition, a mark of his contribution to Leinster's cause over the years. The Leinster Players' Player of the Year Rob Kearney is arguably the form full-back in Europe at the moment and Leinster will aim to get him involved while Sean O'Brien will have plenty of work to do in the wet weather.
Head-to-heads: A Heineken Cup winner with Leinster 11 months ago, Nathan Hines has also been in prime form and will hope to work out the Irish team's line-out. But he'll be up against one of the best in the business in the form of World Cup-winner Brad Thorn, who has impressed since arriving in Dublin. The battle at outside centre will be world class as Aurélien Rougerie faces off with Brian O'Driscoll. Both men are central to their respective team's game-plans, making their duel crucial.
Prediction: Very, very tough to call. It really could go either way. The bookies are giving the sides exactly the same odds. The 'home' crowd will certainly help the French team but it's very difficult to argue with the momentum Leinster are carrying at the moment. Leinster to edge it in extra time!
Clermont: 15 Lee Byrne, 14 Sitiveni Sivivatu, 13 Aurélien Rougerie, 12 Wesley Fofana, 11 Julien Malzieu, 10 Brock James, 9 Morgan Parra, 8 Elvis Vermeulen, 7 Alexandre Lapandry, 6 Julien Bonnaire, 5 Nathan Hines, 4 Jamie Cudmore, 3 Davit Zirakashvili, 2 Benjamin Kayser, 1 Lionel Faure.
Replacements: 16 Ti'i Paulo, 17 Vincent Debaty, 18 Daniel Kotze, 19 Julien Pierre, 20 Julien Bardy, 21 Ludovic Radoslavjevic , 22 Regan King, 23 Jean-Marcel Buttin.
Leinster: 15 Rob Kearney, 14 Isa Nacewa, 13 Brian O'Driscoll, 12 Gordon D'Arcy, 11 Luke Fitzgerald, 10 Jonathan Sexton, 9 Isaac Boss, 8 Jamie Heaslip, 7 Shane Jennings, 6 Sean O'Brien, 5 Brad Thorn, 4 Leo Cullen (c), 3 Mike Ross, 2 Richardt Strauss, 1 Cian Healy.
Replacements: 16 Sean Cronin, 17 Heinke van der Merwe, 18 Nathan White, 19 Devin Toner, 20 Kevin McLaughlin 21 Eoin Reddan, 22 Ian Madigan, 23 Fergus McFadden.
Date: Sunday, April 29
Venue: Stade Chaban-Delmas, Bordeaux
Kick-off: 16.00 local (15.00 BST/ 14.00 GMT)
Referee: Wayne Barnes