Ulster coach Mark Anscombe will know more about the depth of his squad after today’s final Heineken Cup pool match. Qualification for the knock-out stages of the tournament has already been accomplished so the primary agenda this afternoon is to chase a home quarter-final.

A bonus point victory will guarantee that goal irrespective of what happens elsewhere over the weekend but a win alone may not suffice to copper fasten a quarter-final at Ravenhill. There are several co-efficients relating to the outcome of other games that will render the mathematics a little more complex.

Ulster’s ambition has been handicapped by injury, the latest of which denies them a couple of players who have enjoyed a huge impact in their season to date. New Zealand-born fullback Jared Payne has finally succumbed to the groin strain that has been niggling away for some time while his compatriot, Nick Williams suffered a knee injury last week that will see him sidelined for up to two months.

The pair have been outstanding contributors and their absence coupled with that of Tommy Bowe, Johann Muller, Dan Tuohy and Stephen Ferris appreciably increases the magnitude of the task facing Ulster. They have never won a European match in France, their best result in 14 matches there a 35-35 draw with Toulouse in 2000.

Four changes

Anscombe has made four personnel changes and two positional switches. Craig Gilroy moves to fullback with Michael Allen – a very promising centre at school who has been dogged by injury over the past couple of seasons – on the left wing.

Ruan Pienaar is preferred at outhalf to Paddy Jackson, allowing Paul Marshall to start at scrumhalf. The one slightly curious aspect of their halfback shuffle is that Anscombe has named a third scrumhalf, Michael Heaney, on the bench.

Neil McComb’s greater ballast paves the way for a first European start alongside new Ireland squad member Lewis Stevenson with Iain Henderson dropping to the bench. Roger Wilson replaces Williams at number eight.

Despite a sizeable injury list Anscombe is unequivocal about what he will demand from his players this afternoon. “We set out a goal to get a home quarter final, so we’re certainly not resting on our laurels and we’re going to Castres with a job at hand. We want to reward our fans and people with a home quarter final and if we don’t do that I feel we will have let ourselves and the supporters down.

“Like a lot of French teams, they are very strong at home and have only lost one game at home this year. From what we’ve seen of them this year they have a formidable forward pack. We know where our work is going to be at and if we don’t front up then it’s going to be a long day.”

Test for visitors

It’s interesting to note that Castres Olympique have left two of their standout players, secondrow Joe Tekori and diminutive French international speedster Marc Andreu on the bench. They huffed and puffed to beat Glasgow in their last home match, only sneaking home with a late try. They’ll certainly test the visitors’ set piece – Tom Court has been excellent in the scrum and around the pitch – and in scrumhalf Rory Kockett have a very accomplished place-kicker.

There’s no doubt that Ulster will miss Williams’ power and offloading skills, so too Payne’s lines of running and intuitive distribution but they do have the grunt to compete with their hosts. Ulster will need to retain the ambition they have previously demonstrated in their patterns this season because they won’t run over the top of Castres physically. Ulster might just secure victory but the four-try bonus point may be asking a little too much.

CASTRES OLYMPIQUE: P Bernard; M Evans, S Bai, R Lamerat, M Garvey; R Tales, R Kockott, Y Forestier, MA Rallier, A Peikrishvili; M Rolland, C Samson, M Babillot, P Faasalele, P Wannenburg. Replacements: B Mach, S Taumoepeau, M Lazar, J Tekori, T Lacrampe, J Bornman, P Bonnefond, M Andreu.

Ulster: C Gilroy; A Trimble, D Cave, P Wallace, M Allen; R Pienaar, P Marshall; T Court, R Best, J Afoa; L Stevenson, N McComb; R Diack, C Henry (capt), R Wilson. Replacements: R Herring, C Black, D Fitzpatrick, I Henderson, M McComish, M Heaney, P Jackson, C Cochrane.

Referee: Nigel Owens (Wales).

Verdict: Ulster to win.