THE last cut is the toughest. Selecting seven players to release, as he did a week ago, was pretty straightforward for Vern Cotter: all were on the fringes of the squad, with a couple having been brought in largely for experience.

Now, however, the head coach has to drop another nine to get to his final figure of 31 for the Rugby World Cup. Some choices will be made on medical advice, some on tactical considerations rather than purely on individual merit; but nearly all will be marginal calls.

Cotter and his assistants convened last night to review Saturday’s win over Italy and to begin their deliberations on selection. They will complete their discussion today, then the final squad will be announced tomorrow.

The head coach has given next to nothing away. For example, there has been a general presumption, within the squad and out, that he will take all three of the hookers in his current group of 40, but he refused to confirm that at the weekend.

He has yet to decide on the precise split between forwards and backs, and, within the pack, between second row and back row. “I don’t know yet,” he said when asked if he would choose six back-row players from the current group of nine. “It could be five or six. Three or four for locks. We don’t know yet.

“We’ve got players who can play several positions. We’re still waiting for a full update on injuries before we do anything. We’re still waiting to decide if it’s an 18-13 or 17-14 split.”

If Cotter does go with 18 forwards, that means dropping only four from his present group, with prop Gordon Reid and three back rows - Adam Ashe, Hugh Blake and Alasdair Strokosch - looking the most vulnerable. If he opts for just 17, the additional man to go could be Rob Harley or John Barclay. Harley, who is listed as a lock but is really a flanker, is more versatile, but Barclay is in better form.

The alternative is to include both those men and omit Jim Hamilton, whose departure has been widely presumed. If Cotter is actually thinking of Harley as a flanker, that would leave Grant Gilchrist and the Gray brothers as his three second rows. David Denton can cover lock as well as Harley, but with only four days between the first two pool matches, that looks inadequate.

There is a safety net, of course, in that injured players can be replaced after the squad is named. When it comes to selecting the backs, Cotter will take that into careful consideration, as Tommy Seymour, Sean Maitland and Alex Dunbar are all still on the injury list and yet to play this summer.

Seymour, who dropped out because of a back injury after being selected for the first warm-up game against Ireland, is closest to playing. Maitland, who is returning from a longer-term shoulder injury, may also be able to take part in the final warm-up match, against France in Paris this weekend. Dunbar is further away, and has known since damaging a cruciate ligament in February that he faced a race against time to be involved in the World Cup.

While the option of replacing an injured player is useful, it might be deemed unnecessarily disruptive to the group’s preparation to select such a player, omit another from the squad, then be forced to switch a week or two later. A fully-fit Dunbar would be one of the first names on the team sheet, but it is a big ask to go from seven months’ absence from competition straight into the World Cup.

If only 13 backs make the squad, five will be cut from the current group. Chris Cusiter will be one: having been on paternity leave and then trained with his club, Sale, the scrum-half acknowledged that he would only be called up in the event of injury to one of the other three No 9s, all of whom will be selected. The other backs to be dropped could be Tim Visser, Ruaridh Jackson, Dunbar and Richie Vernon.

If 14 backs go, it could come down to a straight choice between Dunbar and Vernon. It will be a close call between Jackson and Greig Tonks, both of whom cover stand-off and full-back, but Tonks’s ability to slot in at centre may swing it. Visser’s two tries against Italy did his cause no harm, and any doubt about Maitland or Seymour could see him straight back in.

The captain for the tournament, also to be announced tomorrow, will be Laidlaw, with Henry Pyrgos and Gilchrist as his deputies. When Cotter initially announced his squad in June he said he might select two captains, and with such a tight turnaround between the first two matches it is probable that two different men will lead Scotland against Japan then the USA.

But Laidlaw has the most experience, and plays in Cotter’s favourite position for a skipper. So does Pyrgos, who led the team well in Turin, while Gilchrist, who was named captain for the 2014 Autumn Tests before injury intervened, has impressed Cotter from the start.

Scotland squad of 40 to be cut to 31 for Rugby World Cup. Final squad announced Tuesday afternoon in Edinburgh.

Backs (18): Back three: Stuart Hogg, Sean Lamont, Tommy Seymour, Sean Maitland, Greig Tonks, Tim Visser. Centres: Mark Bennett, Peter Horne, Matt Scott, Richie Vernon, Alex Dunbar. Stand-offs: Finn Russell, Duncan Weir, Ruaridh Jackson. Scrum-halves: Greig Laidlaw, Henry Pyrgos, Sam Hidalgo-Clyne, Chris Cusiter.

Forwards (22): Props: Alasdair Dickinson, Ryan Grant, WP Nel, Jon Welsh, Gordon Reid. Hookers: Ross Ford, Stuart McInally, Fraser Brown. Second row: Grant Gilchrist, Jonny Gray, Richie Gray, Jim Hamilton, Rob Harley. Back row: Blair Cowan, David Denton, John Hardie, Ryan Wilson, Josh Strauss, Adam Ashe, John Barclay, Hugh Blake, Alasdair Strokosch.