Townsend faces dilemmas before his 'most significant' selection

On the road to this point, he has lost a few warriors - Jamie Ritchie and Jamie Dobie after the Calcutta Cup and now Scott Cummings and Gregor Brown, too.

That's a stellar cast list in the casualty unit, particularly the three forwards and especially the locks, who have been immense in Scotland's recovery from the despondency of Rome.

Elliot Millar-Mills, previously unsung, had such a terrific impact off the bench against England and Wales that his injury can now be categorised as a blow.

In keeping with this trippy, but utterly wonderful, championship, Duhan van der Merwe is also out, a loss that would have been seen as an absolute calamity not that long ago.

Now, given his bit-part season, it's merely regrettable but entirely salvageable. Even on his very best form it's hard to see how he would have shifted Graham, scorer of two tries against France, and Kyle Steyn, arguably the player of the entire tournament so far.

In the four games, Townsend has started two different full-backs and three different left wings. He has changed his hooker from Italy to England, England to Wales and Wales to France - Ewan Ashman, George Turner and Dave Cherry all getting the nod at different times.

He's had three different second-row combinations and three different back-rows. Some of this has been forced by injury.

His first three benches have had a 5-3 split before he switched to 6-2 against France, a day when Rory Darge, the brilliant flanker, ended up playing centre alongside the inspirational captain, Sione Tuipulotu.

So what now? Ireland were blown away by France, sneaked home against Italy, were utterly imperious against England and then battled to a win against Wales.

They have issues with their scrum, among other things, but they have home advantage and an astonishing win rate against Scotland.

Does Townsend have many big calls to make for such a momentous game?