Comment: Murray worry underlines Munster's lack of depthErasmus could be forced to turn to long-serving Williams
Perhaps it is the European form-line they carry into tomorrow's European Champions Cup quarter-final against Toulouse or maybe it's the heavy win they enjoyed when the same opponents pitched up in Limerick three years ago, but confidence abounds in Munster this week.
And yet, if the news comes through before kick-off that Conor Murray hasn't made it, the nine-point spread in the Reds' favour will begin to look quite generous and the restlessness will grow around Thomond Park.
For all that he is 30 years old and has played 130 times for his province, next man in Duncan Williams just doesn't carry the same weight as the man he covers.
As yet, the Corkman does not know what role he will play tomorrow but he will have a job to do whether Murray makes it back from his shoulder problem or not. He has come off the bench in all of their European games to date and is probably enjoying his finest season.
Rassie Erasmus looks set to name the Ireland star in his starting XV today, but there is no guarantee that he will play against Toulouse.
Three weeks ago, the Patrickswell native suffered a stinger when attempting to tackle George North at the Millennium Stadium. Joe Schmidt left him out there for almost 15 minutes as his passes dropped and his tackles soaked, before conceding defeat and sending Kieran Marmion into the fray.
Ireland did everything in their power to get him on to the field a week later against England, but his shoulder couldn't live up to the contact.
"Conor trained OK on Tuesday without contact but we fitness-tested him today and felt he wasn't 100pc, if more bruising came on that shoulder and we lose him early in the game, we're vulnerable," Schmidt said when he named his team.
In the end, Marmion and replacement Luke McGrath performed admirably in the win over England and Ireland discovered that as good as Murray is there is an alternative to the Lion.
Munster may end up in the same boat, but while Ireland's resources are thought to be thin in the scrum-half ranks, the Reds have even less to turn to if their main man is out.
That's why they are likely to press him into action and hope for the best tomorrow.
"I don't have to tell you how important Conor is," skipper Peter O'Mahony said this week.
"Obviously he's probably the in-form No 9 in the world at the moment and for any club to lose a player of that calibre is going to alter things.
"You know how good he is. He's very important to us and hopefully he'll be good to go."
If he doesn't make it, a province will turn their eyes to Williams; a man whose relationship with Munster fans has not always been plain sailing.
He has eked out a long career in red, but has never fully earned the trust of his coaches.
The nadir of his relationship with a frustrated Red Army came in the autumn of 2014 when he was booed off the pitch after the Anthony Foley era got off to a bad start against Edinburgh.
"It is difficult, but you wonder at times what are people watching," the late head coach said at the time, arguing his scrum-half had not been protected.
"Duncan gets on with his job, he's very resilient and an excellent player. We want him to develop and we want him to play his natural game."
Later that season, Williams played his biggest game in Munster colours when Murray was ruled out of the pool decider against Saracens.
It didn't go well. He was far from the most illustrious player who under-performed that afternoon in Barnet, but Murray's loss was felt keenly.
At that point, it appeared the scrum-half had little future with the province and Foley opted to bring Tomás O'Leary back from London Irish to increase his options as injury saw Cathal Sheridan move to the margins.
And yet, two years on, it is Williams who is once again ready to step into the breach.
Sheridan was released and then recalled only to suffer a serious injury, while O'Leary secured a mutually-agreed departure earlier this season.
Rassie Erasmus has had to sign Te Aihe Toma from Bay of Plenty while South African Abrie Griesel was promoted from Young Munster and Dubliner Angus Lloyd has joined on loan from Ulster.
For a set-up in the midst of a revival, it is a reminder that there is a thinness to Munster's squad that doesn't exist across the rest of the European Champions Cup quarter-finalists.
There are areas where they can't afford to lose bodies and scrum-half is top of the list.
Yet, after all of the criticism and tough days, Williams has come out the other side and the squad are ready to place their faith in him. "If Conor doesn't pass his fitness test Duncan's been good for us," Jaco Taute said this week.
"He has got a lot of game-time under his belt and sometimes that's the most important thing, being on the pitch and playing so if he has to take up the role he will be ready and we'll be ready. We've been playing a lot with him."
A look at the two players' statistics across this season suggests there is not much difference between the two, but Murray brings so much to the table in terms of leadership, decision-making, defensive impact and composure.
If he doesn't make it through the warm-up, then it will be over to Williams to step up to the plate and give the performance of his career.