Alan Quinlan: 'Return of Vunipola could cause plenty of problems - but Irish back row have the solutions'
Declan Kidney never used to tire of reminding us that "forwards win matches and backs decide by how much".
This evening, that adage is particularly relevant.
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In fact, when you weigh up the trend of Ireland's Tests against the world's best in recent times, and the strengths and weaknesses of this England side, there is one area that looks likely to be more decisive than most - the back-row battle.
Back-rowers have hogged the man-of-the-match gong in this fixture in recent years: Tadhg Furlong's accolade in Twickenham last year ending the four-in-a-row chances for the loose forwards after Peter O'Mahony (2017), Vunipola (2016) and Seán O'Brien (2015) had been singled out for praise.
O'Mahony was the star man in the November victory over New Zealand too, while Wallabies poacher David Pocock and CJ Stander were the first men to be interviewed after Tests 1 and 2 of the summer tour to Australia; Furlong getting the nod in the Sydney decider.
With Billy Vunipola strapped and ready to go, England are an altogether different proposition.
His mere presence spreads reassurance and confidence throughout the group; without him their freight train is missing its driver.
Ireland's back-row will have their work cut out trying to prevent Vunipola punching holes in their defensive line, while protecting Johnny Sexton's channel from the 130kg bulldozer will also be a priority.
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Planning to stop Vunipola building up a head of steam is one thing, actually slowing him down, preventing him from putting team-mates into space, and bringing him to ground, is another.
You need to make special plans for players like Vunipola, limiting their influence by whatever means possible.
His dynamic carries and offloads can turn a tide that will rise all the boats around him.
Our Munster side used to play against Leinster's Victor Costello with similar caution; he was another big man who was incredibly difficult to stop once he got his legs pumping.
For kick-offs, I was constantly reminding ROG not to land the ball within the Leinster No 8's reach.
If you give a man like that, or Vunipola, 20 metres to accelerate before hitting your defensive line you're just asking for trouble.
When Costello was at the base of an attacking scrum you always had to be on your toes, reducing his opportunity to accelerate from the back of the set-piece by whatever means possible.
I was regularly in offside positions, halfway up the Leinster side of the scrum, just to minimise his window to build up any kind of momentum.
You do what you have to do - and hope you get away with it.
It's the same with Vunipola, you devise plans to limit his influence in all sorts of scenarios.
In an ideal world you would always have at least two of your best tacklers - Josh van der Flier in low and Stander or O'Mahony up high - ready to take him down, but England will be seeking mismatches and Ireland need to be prepared for that.
There will be plenty of pressure on the Irish defensive scrum this evening too, particularly on Cian Healy's side. He'll need to at least get parity with Kyle Sinckler on England's put-in.
If Sinckler were to get a good angle up against Healy in the set-piece, Vunipola would be able to control the ball at the base of the scrum and charge down the Irish 10/12 channel.
While Sexton would never shirk his defensive duties, it's a situation you want to avoid.
Vunipola may be a formidable weapon but Ireland don't lack in that department either.
More to the point, while the England No 8 may be excelling for Saracens again there remain doubts around his fitness for Test matches such as these - he has played only four times for England since November 2016 - something that cannot be said of the Irish back-rowers.
There has been no shortage of bumps in the road for Vunipola since making his international debut five-and-a-half years ago; three broken arms and serious knee and shoulder injuries have caused him to miss plenty of big days out for club and country, not to mention a Lions tour.
Vunipola's honesty around his weight issues, injury problems, and concerns over player welfare make him an equally intriguing character off the field too.
"What helped me out massively was the realisation, which I'd had a couple of years before, that I should never define myself by rugby - there really are more important things in life," Vunipola, 26, wrote in his 2018 book 'Wrecking Ball'.
"When I die, I don't want to be remembered for whether I went on a Lions tour or not.
"I'd much rather be known for whether I was a kind or honest person. To me, that's way more important."
Someone who probably benefited from his absence in New Zealand was Ireland's very own No 8 wrecking ball, CJ Stander - who made the bench for the second and third Tests on that 2017 tour.
At 115kg, Stander doesn't bring quite the same mass to the contact areas but he manages to be at least equally dynamic in his carrying.
And while his footballing skills are not quite at Vunipola's level - few are - he makes up for that with his tireless work-rate; consistently hitting in and around 20 carries per game, with his tackle count regularly in the mid to high teens.
When it comes to hitting high tackle numbers, few can compete with Van der Flier, a man who many wouldn't necessarily pick in their first-choice World Cup squad, but equally someone who most, if not all, would worry little were he to play in a Six Nations decider or a World Cup quarter-final.
Another back-rower who has suffered his fair share of setbacks, the 25-year-old has been really impressive since returning from the cruciate injury he sustained just 37 minutes into last season's Six Nations opener in Paris.
Had he not been so unfortunate this time last year, he may well have kept Dan Leavy out of the side for the remainder of the unforgettable campaign, taking the plaudits that his Leinster team-mate was instead showered with.
His physicality in the tackle and carry have improved since his return last September, and while I would like to see him become a bit more confrontational at times - something O'Brien and Leavy have no trouble with - his attributes bring great balance to this Irish back-row, as we saw in the November success against New Zealand.
O'Mahony led the way from the blindside on that memorable night in Dublin, while it was this fixture two years ago, albeit at the end of the Six Nations campaign, that catapulted him into the frame for the Lions captaincy.
His work at the breakdown, ably assisted by the likes of Van der Flier, Stander and Rory Best, will likely be instrumental again this evening.
Tom Curry will be England's primary groundhog with Mark Wilson adding steel at No 6.
And while both players have been in good form for Sale and Newcastle respectively this season, with a combined 13 Tests between them - O'Mahony and Stander each played 10 Tests in 2018 alone - I expect the Ireland trio to win this crucial back-row battle, and a gripping Six Nations opener, despite Vunipola's considerable talents.