Edinburgh, last year's beaten semi-finalists, have no room for manoeuvre. Lose today and it would require a recovery of seismic proportions to see them involved in the latter stages.
A lot has been made of Munster's failure to close out that game last weekend in Paris and it's to be hoped the players will have put it behind them. "All we can do, week to week, is keep trying to build. Keep trying to grow. And keep trying to get better. And on the back of that hopefully the performances will end up having positive outcomes." Coach Rob Penney says before sounding a cautionary note.
" But we don't control everything in the game . Y'know there's another 15 guys on the opposition trying to do exactly the same thing. And if they happen to be better on the day it makes it difficult."
Whatever about better on the day, it can be taken as read that the Edinburgh we see today in Thomond Park Stadium will be better than the side that were kept scoreless and shipped 45 points against Saracens.
Last time the sides met, in Murrayfield in September, Tim Visser skipped in for three tries. But Munster won.
Ian Keatley was the out-half that day and today he wears the mantle of playmaker (10) for the first time in Heineken Cup rugby. In Murrayfield Keatley scored a try and was deadly accurate with the placed ball kicking 3 penalties and two conversions.
Munster will need him to be in a similar frame of mind today.
But central to that victory on September 1st was the end-game defensive performance.
And Munster will need a similar mindset in that department as well today.
Munster: D Hurley; D Howlett (capt), C Laulala, J Downey, S Zebo; I Keatley, C Murray; D Kilcoyne, M Sherry, BJ Botha; D OCallaghan, P OConnell; D Ryan, S Dougall, P OMahony. Replacements: D Varley, M Horan, S Archer, B Holland, P Butler, D Williams, JJ Hanrahan, F Jones.
Edinburgh: G Tonks; L Jones, N De Luca, B Atiga, T Visser; G Hunter, R Rees; J Yapp, R Ford, G Cross; G Gilchrist, S Cox (capt); D Denton, S McInally, N Talei. Replacements: A Titterrell, R Hislop, WP Nel, R McAlpine, D Basilaia, C Leck, M Scott, T Brown.
Referee: Wayne Barnes (England).