Although they are playing on different days in different countries, the fate of both Irish sides may be inextricably linked once the final permutations conclude tomorrow evening before the last-eight draw.
Munster and Leinster, who have shared five of the last seven European titles between them, know that they require victories – most probably with a bonus point – from their final pool games to have any chance of qualification. And, unless Toulon pick up a win in the early afternoon game today to deprive Montpellier of a final-eight berth, it is highly likely that Munster and Leinster will be scrapping it out to secure the last quarter-final slot.
Leinster coach Joe Schmidt has unleashed the heavy artillery for his side's visit to Exeter Chiefs, with deposed Irish captain Brian O'Driscoll passing a fitness test to resume his familiar berth in midfield. Fellow Irish stars Sean O'Brien, Richardt Strauss, Kevin McLaughlin and Eoin Reddan are also restored to his starting XV.
"We need a number of things to go our way to get a four-point win and qualify," said Schmidt, whose side avoided the snow chaos afflicting England after arriving safely in Exeter airport yesterday afternoon.
"We need Montpellier to lose by more than seven points, Toulouse to either win or lose by more than seven points and Munster to lose as well to make sure we were in there.
"I think there is probably some other thing that could happen. I taught English, not Maths. It's beyond me. I want to keep it as simple as possible. I want to present as tough a task to others as possible."
Munster, who have home advantage against a second-string Racing Metro side tomorrow, know that they may only have to match Leinster's result to qualify as their try-scoring tally is currently superior to their rivals' by one.
"If we win on Sunday and get to the quarter-finals it will be looked upon as success, just as it was last year," said Munster assistant coach Anthony Foley ahead of tomorrow's lunchtime clash, for which Ronan O'Gara is suspended.
Ulster, who have already qualified for their third successive quarter-final but need to win for the first time ever on French soil – at Castres this afternoon – to guarantee a Ravenhill last-eight tie, have dropped out-half Paddy Jackson for the clash.