It seems a bit like wringing a dirty mop out on the fire that's just warmed the entire house but after the glow of Cardiff it all comes down to the maths. The Calcutta Cup match swung along lustily but it too added not so much to the romance of a hard game well fought, but to the sums. The scoreboard has always demanded the ability to count. Now we must subtract.
After all the prodigious work of the back-rows - and Justin Tipuric could be added to the starting six from Wales-Ireland for impact and sheer cussed indefatigability, and Courtney Lawes did his normal interpretation of a flanker playing in the wrong row - the title will be decided by the somehow unglamorous calculation of points difference.
Presumably. Italy might beat Wales in round five and Scotland might beat Ireland, and the title could go to England, as long as they beat France. There would be a champion without the nitpicking of subtracting 'Against' from 'For'. That would be tidy, but appears unlikely.
On the assumption that Wales can piece a scrummage together from the wreckage of yesterday - and it wasn't just the injuries to Samson Lee's ankle and Gethin Jenkins' hamstring that caused concern in the set piece against Ireland, but a creakiness from the start - and go to Rome and win some ball on the front foot, the victors in Cardiff should win again. To give up all the rewards of reconstructive surgery and three wins after defeat to England would be unimaginable.
But it would still leave a problem with the maths. Wales improved their points difference by seven to stand at +12 after four rounds. Ireland were reduced by the same amount to +33, which would appear to leave yesterday's losers with a clear advantage. Except that England are now +37. That would not tally with how Ireland started the day, dreaming of an 11th consecutive win - their longest winning sequence - and the grand slam. The maths are still not horribly unfavourable but Ireland's gut feeling must be of crushing disappointment. They gave it one hell of a blast, which may in the end only add to the dismay. If this was supposed to be a contest decided by aerial saturation, a lot of players went off script and stayed grounded. Perhaps it was the sense of a tactic going nowhere but into the safe hands of Leigh Halfpenny and Liam Williams that brought the game back to earth. Whatever, the eye-watering statistic of 289 tackles made by Wales - Ireland made 104 - do not tell of a game played in the air, but of the ball being carried by, well, 289 Irish runners.
If this was supposed to be the anointment of Jonathan Sexton as the peerless king of European rugby, a few Welsh peasants were positively revolting. They made him look as individually out of sorts as their own scrum was uneasy. Sexton missed a shot at goal, kicked a restart out on the full, knocked on and, for an unflappable general, on occasions flapped. He had his head turned from the action once when the ball came his way. It was not the most edifying moment of his career.
It could have been that he was back in action a week too early for his hamstring. But such decisions - to play or not to play - are what define a career. This performance put his rugby beatification on hold.
Dan Biggar filled the vacuum, his hold on the game slackened only slightly - and slightly weirdly - by the knee to Rhys Webb's derriere, the bruise that meant his scrum-half partner was not able to offer him the breathing space that comes with an alternative threat. Webb could not snipe with his customary fast-twitch acceleration and Biggar had to run the show on his own. Given that everybody in red in every position was feeling the effect of those 289 tackles, he was even more important. His drop goal, albeit in the first half when Wales were not yet out on their feet, was masterfully prepared and executed.
On the subject of how arithmetic will have the final say, the statistical record of Wales defending a slender lead in the last quarter is not good. The arrival of Scott Williams - just as he once did against England at Twickenham - seemed to have provided a measure of comfort. An 11-point lead was beyond a wild dream.
When Ian Madigan put a penalty into the corner it looked like a risk, a commitment to seven points when time still allowed for three to do nicely. On came the drive and a couple of yards short of Wayne Barnes's award of the penalty try it was clear that the decision had been correct.
The penalty won by Sam Warburton with six minutes to go was as much about filling time, giving everybody a breather, as about landing the three. Except that it meant Ireland had to score a converted try just to draw. They could not win, but how they battled. It went to a final scrum, which was not what Wales needed. And here came their gift, a penalty beyond the 80-minute mark.
It could well be their last present of the campaign. From now on it's the lung-bursting quest for points in Rome. As little scrummaging as possible; as many tries. The same for Ireland. As much of the old Sexton as possible; as many tries.
England, by the time they kick off against France, will know the score - and how many points they will require. Between them and the title lie France. This is where the maths turns French; so far they have brought nothing but chaos theory to the calculations.
Sunday Indo Sport