IT MAY be too late for the first three rounds of Six Nations games, but the back row battle for Scotland is about to heat up with two of the leading contenders for starting spots in the national side both returning to action for their clubs - giving them two games to play their way into contention for the Calcutta Cup match in Twickenham.

Both David Denton of Edinburgh and Adam Ashe, his Glasgow Warriors counterpart, will fancy their changes of gatecrashing the current Scotland setup if they can prove their fitness, for Denton in Cardiff tomorrow and for Ashe in Cork this evening.

For Ashe, it was perfect timing in more ways than one. It is not just his personal ambition that his well served by his return this week, but with Glasgow Warriors struggling to complete their squad, his appearance at training must have come as a welcome sight for Gregor Townsend the head coach.

He has 12 players in the Scotland squad, three potential replacements on duty with the Under 20s, two banned and eight injured, to leave the club really struggling and having to use Alex Toolis, whose twin bother Ben is in line for his debut Scotland cap, on a loan deal from Edinburgh and give him a place on the bench.

Ashe slots into the side slightly out of position at blindside flanker instead of his preferred berth at No8, allowing James Eddie to move forward to the second row where Jonny Gray and Tim Swinson are starting for Scotland and Leone Nakarawa is serving a ban.

The selection problems mean that three players, Connor Braid, the Canada internationalist who has signed a deal to return to the club from London Scottish, Murray McConnell, the scrum half, and Will Bordill, the flanker, will all make their first starts for the club. Toolis, Tommy Spinks and D'arcy Rae are all in line for their first action in Glasgow colours if they come off the bench.

"After last weekend's win over Ospreys we now face another of the in-form teams in the Guinness PRO12," said Townsend. "They are sitting second in the league, just four points behind us, so we're well aware of the importance of this game. A number of players could make their debuts for the club this weekend, which is a big opportunity for them to show what they can do, and we're also delighted to welcome Adam [Ashe] back."

Edinburgh have also been forced into changes, with Ben Toolis and Hamish Watson both being promoted to the Scotland squad, they have had to shuffle the back row with Denton starting and Roddy Grant and Mike Coman both moving positon to accommodate him.

In the backsm Tom Heathcote pays for his kicking performacne against Ulster last week by dropping to the bench with Jade Te Rure taking over the fly half slot - a role he occupied in the game they won against the Ospreys. "I take a lot of pride in so many of the Edinburgh youngsters being in the national squad," said Alan Solomons, the head coach. "We have to find a way to win without them."

Munster: JJ Hanrahan; A Conway, K Earls, D Hurley (C), R O'Mahony; I Keatley, D Williams; J Ryan, E Guinazu, BJ Botha, Donncha O'Callaghan, B Holland, J O'Donoghue, S Dougall, CJ Stander. Replacements: N Scannell, D Kilcoyne, S Archer, Dave O'Callaghan, P Butler, N Cronin, A Smith, I Dineen.

Glasgow: P Murchie; N Matawalu, R Vernon, F Lyle, D van der Merwe; C Braid, M McConnell; A Allan, P MacArthur, R de Klerk, J Eddie, A Kellock (C), A Ashe, W Bordill, J Strauss. Replacements: D Hall, J Yanuyanutawa, D Rae, A Toolis, T Spinks, G Bryce, L Jones, R Hughes.

Referee: N Owens (Wales)

Cardiff Blues: J Tuculet; R Smith, C Allen, G Evans, T Isaacs; R Patchell, L Williams; S Hobbs, M Rees (C), A Jones, F Paulo, J Hoeata, J Turnbull, E Jenkins, M Vosawai. Replacements: K Dacey, T Davies, T Filise, L Reed, M Cook, T Knoyle, G Davies, A Thomas.

Edinburgh: J Cuthbert; D Fife, S Beard, P Burleigh, T Visser; J Te Rure, G Hart; R Sutherland, N Cochrane, W Nel, O Atkins, A Bresler, M Coman (C), R Grant, D Denton. Replacements: S Mcinally, G Shiells, J Andress, F Mckenzie, H Blake, N Fowles, T Heathcote, A Strauss.

Referee: D Philips (Ireland)