Leinster must be on full alert as London Irish have been able to recall their twin threats Topsy Ojo, for the first time this season, and Sailosi Tagicakibau, for the first time since November, for what Brian O'Driscoll called a 'winner-takes-all' contest at Twickenham this evening.
The champions are just one win away from their first home Heineken Cup quarter-final in Michael Cheika's five-year reign.
It could be the longest 80 minutes of their season as Ojo and Tagicakibua offer the best back three in the Guinness Premiership on either side of full-back Delon Armitage.
Leinster are in the driving seat, standing five points clear of London Irish, requiring just a losing bonus-point to guarantee their graduation to the last eight or four points for a top-four seeding and a date at the RDS on the second weekend in April.
Anything less than a victory will come as a massive blow to a collection of players fully intent on defending their title. They have spent a decade developing a winning mentality.
"We want to win the Pool. We have that destiny in our hands," echoed Brian O'Driscoll.
Leinster have a number of Ireland internationals, namely Brian O'Driscoll, Gordon D'Arcy and Shane Horgan, with fond memories of the home of English rugby.
They will not lack know-how on the nuances of the stadium or the experience of having won big matches at Twickenham. D'Arcy shredded England there in 2004 and Horgan stretched for that exquisite winning try to ensure a Triple Crown in 2006.
However, London Irish are a wounded animal, one equipped to strike with venom. At their best they have a world-class scrum and lineout platform to release what can be a lacerating attack.
They would have seen a glimmer of hope in Leinster's concession of two tries to Brive last Saturday. It was certainly a blip for what is the best defence in the competition.
"We pride ourselves on our defence. We had only given up three tries before the two sloppy ones we gave up against Brive. It is the cornerstone of all victories," issued O'Driscoll.
"We've put extra emphasis on making sure our defence is better this weekend, particularly considering how London Irish need the four tries."
When the Exiles arrived at the RDS in round one last October, the onus was on Leinster to make the running, to break down a rock-solid London Irish defence at a time when the champions were not quite up to speed.
That night Toby Booth's men were content for their openside Steffon Armitage to spoil the breakdown, for their lineout duo of Nick Kennedy and Maynooth's Bob Casey to rule the airwaves and for Peter Hewat and Ryan Lamb to kick Irish to a 12-9 win.
Their problem is that the boot is now on the other foot. The Exiles have to shoulder the pressure of, not only having to make the game happen, but having to go out and strike for four tries. Their world class back-three makes this a possibility.
Cheika has taken the proactive move of giving game time to those who badly need it, in the debatable selections of Bernard Jackman over John Fogarty, CJ van der Linde over Stan Wright and Shane Jennings over Sean O'Brien.
Perhaps Fogarty can consider himself the most unlucky of those to lose out. He has been finding his men with pleasing regularity at the lineout and has not given an inch in the scrum.
Maybe, it is Jackman's greater threat with ball in hand against Fogarty's superior work on the ground that is a reflection of Cheika's plan to carry the game to the Exiles.
London Irish: D Armitage; T Ojo, E Seveali'i, S Mapusua, S Tagicakibau; C Malone, P Hodgson; C Dermody, D Paice, F Rautenbach, B Casey (capt), R Thorpe, S Armitage, C Hala'Ufia.
Leinster: R Kearney; S Horgan, B O'Driscoll, I Nacewa; J Sexton, E Reddan; C Healy, B Jackman, CJ van der Linde, L Cullen (capt), N Hines, K McLaughlin, S Jennings, J Heaslip.