It is the oldest cliché in rugby's book that forwards win games and backs merely decide by how much.

But age has not diminished the truth of it as far as Gregor Townsend is concerned. Hence the Glasgow Warriors coach's selection of a bench for tonight's crucial Heineken Cup clash with Cardiff Blues that is heavy on piano shifters and rather light on piano players.

The choice of six forwards and just two backs - and both half-backs at that - as replacements suggests that Townsend does not expect his side to be zipping the ball towards the wings at every opportunity. In fairness, it is also the strategy he has used in other games recently, but in the European context it was always likely to recall his approach against Northampton last year - his first Heineken Cup match in charge of Glasgow - which appeared to backfire when the Warriors suffered such a spate of injuries behind the scrum that Chris Fusaro ended up doing a shift in the centre.

"It's what we have done in our last three games," Townsend explained. "Against Connacht [on Nov 2] the two backs didn't come on at all. We obviously have scenarios in mind to deal with the possibility of having more than two backs injured. Forwards like Ryan Wilson have the capability to play in the backs. The good thing is that we have flexible players as well. Niko Matawalu has played as full-back and on the wing, so there are players who can move positions, which is great."

Townsend's side gave themselves a valuable confidence boost when they came from behind to beat Ospreys 28-16 in their RaboDirect PRO12 clash at the Liberty Stadium a week ago. Remarkably, though, only six of the players who began that match will be in the starting XV at the Arms Park this evening. Injuries have played a part in that scenario, but Townsend pointed out that other factors had been more significant.

"I had a lot of thinking to do picking the side," Townsend said. "There were a number of players becoming available, with the guys who had been rested last week after the November Tests and with the Fijians [who had been involved in their country's match with the Barbarians] coming back into the mix. It was a tough team to pick."

At least one decision was easy, though. With Peter Horne out for the entire season, Sean Lamont sidelined by an ankle ligament problem and Mark Bennett absent on Scotland sevens duty, Alex Dunbar has timed his return from injury brilliantly and goes straight back into the side. Dunbar, who made his Test debut on Scotland's summer trip to South Africa, had been absent for six weeks since damaging his shoulder in Glasgow's opening Heineken Cup match against Toulon in October, but Townsend had no hesitation about pitching the 23-year-old midfielder straight back into action without the benefit of an RBS Premiership outing to sharpen his match fitness.

Townsend said: "He has worked really hard in training. He could have been available last week, but we felt that he just needed a little bit more work in the gym. But he has been going really well for the past two weeks and it's great to see him back again. He was in excellent form before his injury and he is in great nick again. We play a lot of games at training and we do full contact as well. He has been well tested over the last couple of weeks."

Townsend pointed out that Cardiff try to keep the ball alive as much as possible on their artificial surface. The likelihood is that Glasgow's back-row replacements, Tyrone Holmes and Ryan Wilson, will make their appearances earlier rather than later. "We know we're going to have to defend and try to get the ball back off them," he said. "It's reassuring to know that we have another openside on the bench and a No.8 there as well."

The regular complaint of Cardiff supporters down the years has been that their side has punched far below its weight. The Blues' lowly PRO12 position - they are in ninth place, with just three wins in nine games - is bizarre, given the calibre of players on their books, but Townsend pointed out that the team that plays in Europe is often far different from the one that turns out for domestic games.

That much was clear when Cardiff, bristling with recent Lions tourists in the shape of Sam Warburton, Alex Cuthbert, Leigh Halfpenny and Gethin Jenkins, scored a sensational 19-15 home win against reigning champions Toulon in the last round of the competition. However, their firepower today is dimished by injuries that have ruled Warburton and Jenkins out of the game. On top of which, Lloyd Williams and Rhys Patchell, their influential half-backs, were only confirmed after coming through fitness tests earlier this week.

Giant lock Chris Dicomidis, newly signed from Pontypridd, will make his Blues debut tonight, becoming (it is believed) the first Cypriot international to make an appearance in the Heineken Cup. "He is an experienced club player," said Blues director of rugby Phil Davies. "What a challenge and opportunity this is for him to show he is a top player.

"The last few weeks have been a positive for us. There have been some good periods when we have been consistent and it's an exciting challenge for us with some players coming back. Hopefully we can have the same kind of atmosphere as we had for Toulon and reproduce that level of performance."

There will be a minute's silence ahead of tonight's game and Glasgow players will wear black armbands as a mark of respect for the victims of last weekend's helicopter crash in the city.