Accepted wisdom says that while attack wins matches, defence wins championships. If the adage holds true, then Welsh rugby supporters should be starting to feel very excited over their side's chances of reaching a first World Cup final.
Rugby can be a peculiar sport. Kicking the ball out of play, for instance, is usually regarded as a canny tactical move, and routinely attracts cheers from the crowd.
There are other quirks, too. When Wales beat a much-fancied Ireland side yesterday, to clinch a semi-final place against France next weekend, arguably their most important player did not carry the ball for as much as one yard in the whole game.
If he even had his hands on the ball at all, most people will probably have missed it.
Yet Sam Warburton, the Wales openside flanker and captain, was still highly influential.
Much was made in the build-up to the meeting between the two leading Celtic nations about the impending battle between the opposing No 7s.
Sean O'Brien, the European player of the year, was getting the majority of the air-time, mainly on the back of successive man of the match awards for Ireland.
Despite fine personal form of his own, Warburton has managed to fly below the radar to a degree, probably because he is a quiet defensive assassin.
He does not sing the Welsh national anthem before the game. If he can help it, he prefers not to speak to anyone else in the dressing room before kick-off. Warren Gatland, the Wales coach, made that particular habit a little difficult to maintain when he made him captain ahead of the World Cup.
Being understated is part of the job-description. The best openside flankers pride themselves on the quality of the work they do which goes unseen.
Only Adam Jones, the shaggy-haired titan at tight-head prop for Wales, did as little as Warburton did with the ball in hand against Ireland.
Yet in leading the Welsh effort at repelling the Irish attack, he starred. Warburton made 18 tackles during the game.
His back-row colleagues were similarly tireless: Dan Lydiate, the blindside flanker, made 24 tackles, and Toby Faletau, the No 8, made 13. Between them, the Wales back row did not miss one tackle in the match.
The Welsh defensive effort had the fingerprints of Shaun Edwards, their assistant coach, all over it.
Edwards was a rugby league great, and his defensive strategies borrow greatly from the 13-man code.
Defences in union do not have to retreat 10 metres, as they do in league, so if they rush up at the same pace as they do in the other code, the effect can be suffocating. That was clear to see yesterday by the amount of times the commentators praised Wales' "rush" defence.
And Edwards was well prepared to face the Irish. Even before the tournament started, he had analysed their defensive pattern, via his newspaper column in the UK's The Guardian.
"The Irish idea is to hold the ball carrier off the ground after the tackle and then rob him," he wrote.
Wales, by contrast, prefer to tackle low, take the ball-carrier to ground sooner, and then jackal for the ball on the ground. With jackals like Warburton, it is easy to understand why.
While England may have crashed out with barely a whimper against France, they will at least have some presence in the semi-finals.
Intriguingly, the defence coaches of both Wales and France are Englishmen whose background is in rugby league, with Dave Ellis tasked with out-thinking Edwards.
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