Munster need a historic performance as Earls blow firmly tips the balance
Munster's head coach Johann van Graan speaks frequently about resetting to zero at the start of each week as a way of shifting focus from one match to another.
All the work that's gone in to negotiating a difficult pool and overcoming Edinburgh in a tough away quarter-final has them back at level-par for the last two seasons. Only now can their progress be measured.
A third successive semi-final exit is expected, but there is an inner belief among the travelling party that they can stun Saracens and get the job done.
That confidence may have been dented by the news of Keith Earls' unavailability.
The winger joins Joey Carbery on the margins and they will both be missed.
Those two players have contributed as much as anyone to the cause; their team-mates owe them a performance.
And they owe it to themselves. Two years ago their rollercoaster of emotion ran out of rails against Saracens at the Aviva Stadium and 12 months on they were beaten before they got going against Racing 92 in Bordeaux.
To reach this stage three times in a row is a significant achievement, but sport is unforgiving and they don't sing songs for semi-finalists.
Munster's reputation was built on their twin successes of the 2000s which were earned on the back of heartache. This team will feel they have suffered enough.
Emotion and a vocal visiting support in the expected 18,000 crowd will only carry them so far, today they need to strike the correct balance between frenzy and control to take the next step.
Such is the quality of their opposition, they could play out of their skins and still lose but their focus should be on playing out of their skins. The result will fall the way it does.
They boast the best defensive record in the tournament, but meet the best attack.
Their scrum and lineout have been weapons, but Saracens are strong in both departments. Their ball-carriers are capable of domination, but the home side contain some of the best collision-winners in the business.
So, the leaders in this Munster team must take control of their own destiny.
There are days when Peter O'Mahony finds himself at the bottom of rucks and unable to affect the general play, but this cannot be one of those.
Conor Murray must cast off the shackles of his injury and produce the performance he's been threatening for the last couple of weeks.
CJ Stander cannot be a blunt instrument, he has to make gains and be clever with his footwork or else the black wall will suffocate him.
Sarries are superb, but they are human. Maro Itoje concedes too many penalties, Owen Farrell dislikes being put under duress as much as the next man.
They have no recognised openside and they've picked a team built for a high-tempo game when it's their control that gives them the edge.
If Munster can start fast they'll have a shot.
Against Edinburgh they hung in there for 70 minutes and took their one chance when it came. This has to be different.
Van Graan and Felix Jones have to have something they can bring to the party to surprise their hosts.
In 20-degree heat and against a team with a stellar bench there is no way Munster can white-knuckle their way through. Low-risk won't suffice.
It is a fascinating study into this team that achieves so much in the winter months but runs aground in the spring and early summer. Today is a chance to alter that perception.
It may be that they are the fourth-best team in Europe and there is no shame in that, but so many of this group of players were raised on a diet of silverware that they expect to follow in the footsteps of the men who went before them.
Losing Earls may make it a bridge too far but their mission is to go out and do themselves justice with the best performance of their season, of this era, and see where it leaves them.