In naming a 42-man training squad for the World Cup on Tuesday Gregor Townsend officially launched squad-picking season.

Squad-picking is a pursuit that will inflict many in the coming months. The stricken find themselves incapable of getting through a day without scribbling down the names of the 31 men they think will board the plane for Japan before starting an argument in their own head and ripping up their list and starting again.

It's a Groundhog Day for geeks, with this scribbler firmly in the ranks. Surveys suggest that each victim gets through hundreds of different versions of the squad before they eventually come out of their trance-like state.

Townsend is the only one who has to do it for real and that process has now started. The provisional squad has been named with room for two more - a lock (Richie Gray would be the favourite) and, most probably, a wing (Lee Jones may be the one in the frame if he can prove his fitness).

The 44 will be whittled down to 31, which will take some doing. It's fair to say that of all of Scotland's World Cup squads since the tournament began back in 1987, this one demands more debate than any other and, as a consequence, will be the toughest of all to pick.

How does the numbers game add up?

A natural starting point in all of this is whether Townsend intends to go with a split of 18 forwards and 13 backs or, as Vern Cotter did four years ago, 17 forwards and 14 backs. The former would give him the option of an extra prop or an extra back-five player in the pack at the expense, perhaps, of a wing.

If Townsend knows which way he's going to go then he's not letting on. In reality, he must be open-minded. There's a long way to go, but right now, there's arguably 26 guys who can be considered close to certainties barring any mishap between now and 3 September, the day of Townsend's announcement.

That still leaves a lot of talking points. Jamie Bhatti and Gordon Reid are in a fight to be the fifth prop. With Jonny Gray and Grant Gilchrist virtually on the plane there will be one more out-and-out second row chosen (Gray senior and Ben Toolis are in competition there) with a fourth man picked as a second-row with the capacity to cover back-row. Four years ago that job fell to Tim Swinson. The 2019 version looks like Sam Skinner.

The back-row is where the main conundrums exist. John Barclay, Hamish Watson and Ryan Wilson will travel, but that only leaves two, possibly three, more slots, depending on how Townsend wants to cut it.

If it's only two positions up for grabs you have Jamie Ritchie, Magnus Bradbury, Blade Thomson, Josh Strauss, Gary Graham and Matt Fagerson competing for them. Thomson is the unknown at Test level. The Scarlet is only now making his comeback following a prolonged period out with concussion. He's got the game to force his way in. Ritchie was outstanding in the Six Nations. Strauss has the grunt. Fagerson is fast improving. Graham is the outsider of the lot, but he has a belligerence about him that gives him a chance of causing a surprise.

That's a decent set of options for Townsend. At half-back, things are straightforward. Duncan Weir is playing the best stuff of his life with Worcester but he needs an injury to Finn Russell or Adam Hastings to make it. The only question at nine will be on match day. Does Greig Laidlaw start ahead of Ali Price? If not, does the captaincy revert to Stuart McInally or Barclay? George Horne will be in Japan as the third nine with the livewire capability of pushing the other two all the way.

Tinker with Taylor?

Townsend listed nine centres that have not made his squad. That's an illustration of how brutal the selection was and will be again when he has to reduce the numbers further. Duncan Taylor hasn't played rugby all season and hasn't worn the Scotland jersey for almost two years because of a catalogue of injuries. If he didn't have bad luck he'd have no luck at all.

You might call him the forgotten man, but Townsend hasn't forgotten. Taylor, fit and firing, is massively important to the coach - and Townsend makes no secret of that. Taylor can play 12, 13, on the wing and at full-back. He's the very definition of versatility and his presence would mean that Townsend can play around with his numbers knowing that he has a guy who can don most jerseys in the backline and deliver in each one.

Of all the intriguing questions the one of most significance and spin-off impact surrounds Taylor and his attempted journey back to rugby. He returns to light training this week. Those opening warm-up games in August will be the making or breaking of him.

Sam Johnson has to be a shoo-in. Huw Jones, too. If Taylor makes it, there will be a maximum of one more centre with a battalion of contenders. Pete Horne, Nick Grigg and Chris Harris are firm favourites of the coach, but Northampton's Rory Hutchinson has the appearance of a bolter every time you see him. This is not going to be easy.

Four wings made it in 2015. Four might make it again, but this is where the Taylor Factor comes into play again. If Taylor travels then Townsend might get away with picking just three wings while adding another forward. Darcy Graham has shot himself into the must-pick category. Sean Maitland and Tommy Seymour are the other two. Both can play 15 if pushed. Blair Kinghorn ought to make it, but he's by no means a banker for inclusion.

In the selection process the more that Townsend's brain is fried the better. The wider squad assembles next month. In the relative blink of an eye 31 of them will be in Japan.