GLASGOW Warriors’ strength in depth is set to be put to a severe test tonight when they bid to extend their unbeaten start to the season in Cardiff. Gregor Townsend has rung the changes to his starting line-up for the game against the Blues, in some cases because of injury but in others by choice, with the back division in particular looking relatively inexperienced at this level.

Stuart Hogg, Tommy Seymour and Peter Horne all hold on to their places from last week’s win over Leinster, but Horne moves from stand-off to centre, while the other four backs all make their first start of the season. In fact, in the case of centre Nick Grigg it will be his first competitive start for the team after making his debut off the bench last season.

Grigg and Horne replace Alex Dunbar, who is rested, and Sam Johnson, who is injured. Lee Jones takes over from Leonardo Sarto on the left wing, Ali Price stands in at scrum-half for the injured Henry Pyrgos, and Rory Clegg is included at stand-off.

Mark Bennett is included in the squad for the first time this season after his post-Olympic rest, and his attacking verve seems certain to be called on against opponents who have also won their two opening games in the PRO12. Josh Strauss returns from injury to wear the No 8 jersey in a pack that is likely to be without Simone Favaro for several weeks as a result of the shoulder injury he sustained against Leinster.

The selection of Grigg in particular is a big call, but Townsend explained he has every faith in a player who is one of the shortest members of the squad at 5ft 9in and who first came to his attention by way of a highlights reel. “Nowadays you get a number of agents in the Southern Hemisphere that pass on players that are Scottish-qualified, and you have a good look at them - and there was something there,” the coach explained. “So we brought him in on trial and he got a partnership contract with Stirling and the academy.

“He did really well. He changed body shape, he was involved in the sevens for a while, and he played really well for Stirling, so he earned his pro contract.

“We've been really pleased with how he progressed in pre-season. He was unlucky against Harlequins - he got knocked out, so he missed the Gloucester game. He played well against Canada, so I've been waiting for an opportunity to give him a run.

“We have full confidence in him. What he does really well is tackle - he’s a very good low tackler. He's obviously not played that many games, but from what we've seen he'll cope very well.

“In terms of attack, he runs well with the ball and has very good footwork. He's been breaking his personal speed times at training in the last couple of weeks, so he's in the best shape to make the most of his opportunity.”

Grigg, who turns 24 on Sunday, was born in New Zealand but is eligible for Scotland thanks to a grandfather from Ayrshire and has represented the national sevens squad. Far from being daunted by making his debut in such a high-profile game with that 100 per cent record at stake, he insisted he was up for the challenge.

“It makes it all the better, I think,” he said. “Obviously there is that element of nerves and stuff, but I like to have a bit of nerves before a game, because it really pushes you to excel and perform at that level. So, fingers crossed I’ll give it my all and see how it goes.”

Zander Fagerson’s younger brother Matt, a Scotland age-group international, is travelling with the squad, while Finn Russell will turn out for Ayr today in his first game back after being injured in last season’s semi-final and could come into contention for a place in the team to play Ulster at home next Friday. “Being able to test out in an unstructured environment should mean he’s available to us the following week,” Townsend said of Russell. “We always looked at him playing a club game.

“If it means two or three club games, that will depend on his form and fitness and how he reacts to contact. He’s done contact for two weeks now; he’s looked good in training.”

Cardiff coach Danny Wilson has gone with three opensides in the back row, including 2013 Lions captain Sam Warburton, who comes in for his first start of the season. Welsh internationals Matthew Morgan, Josh Turnbull and Lloyd Williams have also been selected in a starting line-up that shows four changes from the one that won 24-23 in Munster last week.

Cardiff Blues (v Glasgow Warriors at BT Sport Arms Park, tonight, 7pm): M Morgan; A Cuthbert, C Allen, R Lee-Lo, T James; G Anscombe, L Williams; G Jenkins, K Dacey, T Filise, G Earle, J Turnbull, S Warburton, J Navidi, E Jenkins. Substitutes: M Rees, R Gill, S Andrews, M Cook, N Williams, T Williams, S Shingler, B Scully.

Glasgow: S Hogg; T Seymour, N Grigg, P Horne, L Jones; R Clegg, A Price; G Reid, F Brown, Z Fagerson, T Swinson, J Gray, R Harley, R WIlson, J Strauss. Substitutes: P MacArthur, A Allan, S Puafisi, G Peterson, L Wynne, G Hart, M Bennett, R Hughes.