The clash between Brad Thorn and Nathan Hines will be central to the outcome on Sunday, writes LIAM TOLAND

WITHOUT DOUBT, the grand piano that is Brad Thorn and the upright piano that is Nathan Hines is the clash of the weekend, in the match of the weekend – possibly the match of the tournament.

For Leinster to win they must dominate physically – of that there is no doubt – but to get past ASM Clermont Auvergne in Bordeaux they must get their hands free. If Leinster get sucked into multiphase-offering breakdowns and not freeing their hands in the heavy traffic that is Aurélien Rougerie, Wesley Fofana, Jamie Cudmore, Julien Bonnaire et al, then like Saracens and many others, they may dominate possession but they will not win.

Where can Leinster damage Clermont? Few opportunities offer themselves but the big Georgian David Zirakashvili is one. His work-rate around the park is sensational, in the John Afoa tackle count range, and he’s impressive defensively in open play, as he showed against livewire Saracens hooker Schalk Brits.

Around the breakdown, just like Afoa, he does untold damage. He may not last 50 minutes but in that time his scrummaging can be exploited. He hits very square and powerfully but against Juan Figallo of Montpellier he was far too easily turned inside and popped up in the air. If that happens it’s down to English referee Wayne Barnes to interpret.

The best way to defend the opposition backrow and backline at scrum time is to destabilise their scrum. By half-time Saracens had won four penalties over the Clermont scrum but failed to maximise – Leinster won’t.

The opening scrum against Montpellier on 64 seconds last Friday night went as above and is very telling. French referee Romain Poite allowed it to evolve, Barnes won’t. This pattern continued until finally on the fifth scrum, Zirakashvili drops and Poite calls a penalty. After 25 minutes, on their sixth scrum, he’s mangled again.

Barnes will be crucial. It stunted Clermont’s attacking backrow options no end and neutralised a serious backline. Cian Healy will be primed but needs his backrow and there’s no doubt part of the reason for Thorn’s inclusion is his world class role in the scrum. Clearly Clermont will have spotted Zirakashvili struggling but it has been a constant all season. They also have what appears to be a step back on the hit call to get a cheap free.

In defensive lineouts they compete through Bonnaire in particular but Hines can do damage. Pending field position, they sack the opposition’s lineout maul the old-fashioned way, by placing Hines’ feet well across the line, engaging high on the Leinster shoulder and then he pulls it all down on himself. Very brave, and Leinster will need a transfer from the catcher to avoid getting sacked.

Clermont oscillate from short to long, to front peels, to rear peel, to off the top lineout ball, which is incredible variation, and , Brock James can kick them in to five from the line, where they adore the lineout maul.

When in doubt they will always target Bonnaire but both hookers’ flight trajectory would be a concern under the pressure Leinster can exert on Clermont.

In examining their style, David Skrela’s absence for James changes things. This is no bad thing as James will give us an insight into the soul of Clermont’s playbook.

There is no real discernible style to Clermont outside of “Le Petit General” Morgan Parra mimicking his Ulster counterpart, Ruen Pienaar, in commanding everything with a pack that pummels everything and an outhalf (James) who kicks almost everything. I wonder how many opportunities go abegging for Clermont’s backline?

With such quality in Leinster’s back three and especially Rob Kearney, there is less advantage in targeting him but James has an array of torpedoes – diagonal, Garryowen, grubber and the very dangerous cross-field kick to Sitiveni Sivivatu and Julien Malzieu, which will keep his pack going forward and Leinster’s gasping for air.

They do set up a statue off the ruck, with Parra generally targeting a spot pass to get to wider runners, with the result the same: get to the gainline fast and dominate the tackler and reconfigure.

It took 37 minutes before outside centre Regan King was passed the ball last Friday. Rarely will they force a play (very un-French like) and are happy to attack when the odds are theirs, which is a little at odds with Lee Byrne’s Welsh instincts. Although rejuvenated, he is simply not in Kearney’s class and will, I feel, try to over egg the pudding through his own individual counter attacks; advantage Kearney.

As important as Hines is, Clermont’s man is Rougerie – who like Brian O’Driscoll is right on cue for everything. He chases kick-offs like a blindside (and wins some of them), he runs superb lines off the ball, he is immense in the breakdown and when carrying, can take three defenders to even slow him down, which provides yet another pitch battle of intrigue between himself and O’Driscoll.

Defensively they are very patient, filling the field and don’t quit on the blindside, which is always formed and hunting both ways. They rarely commit more than two to the breakdown and swallow up the ball-carrier, happy to allow an eventual recycle as the defence rearranges.

Rougerie’s work at the breakdown is spectacular in his counter ruck and sheer nuisance. It is at the counter ruck Leinster may trouble Parra, who is very comfortable at the base, taking his time behind a massive pack. Leinster can get at him here.

This brings me back to the pianos on show this Sunday. I’ve long been an admirer of Thorn, his work-rate, his technique and especially his after-tackle actions as the ruck develops; christening him the “Grand Piano” of the rucks. However, to limit Hines to piano status is a mistake as he is, at 35, amongst the best and most complete secondrows in the world.

Don’t get fooled by his jersey pulling and general destructive play. There is a very sharp rugby brain in there and he appears to run their lineouts, but his leadership goes beyond that. His soft hands are a joy to behold, allied to his use of space in the tackle. Watch his offload to Rougerie’s hard line in the lead up to Byrne’s try against Saracens. The only downside is the inclement weather forecast as this will bring errors from his offloads; what a player.

Clermont are a team that can do almost anything but what makes them so dangerous is they choose not to; playing within themselves, bullying the away opposition. Leinster are too long in the tooth to fall on the bully’s sword but the game will be in the balance right to the end.

As for me the weekend starts with a Guinness world record assault; abseil off Limerick's Clarion Hotel for Age Action; check AgeAction.ie