There is something unique about the European double header that exists almost nowhere else in rugby.

In a game where even the tiniest adjustment can shift the momentum of a match, the double header presents an opportunity like no other for the best coaches to show their analytical acumen.

Joe Schmidt may have been under fire in the past fortnight as people try to grasp why Ireland were unable to break their World Cup quarter-final hoodoo. Yet these were the types of situations where he thrived.

In his first two seasons at Leinster he was able to produce a 23-point swing and then a 30-point swing in back-to-back games against Clermont (²⁰¹⁰⁄₁₁) and then Bath (²⁰¹¹⁄₁₂).

While he could not do it a third time – Clermont won both meetings in ²⁰¹²⁄₁₃ – there were still few better than Schmidt at spotting the areas where he could gain an advantage.

The year after Schmidt departed, Leinster were stunned by Northampton, losing 18-9 a week after sticking 40 points on Saints at Franklin’s Gardens.

Get the latest update on injuries from assistant coach Robin McBryde ahead of Saturday's #ChampionsCup clash with Northampton Saints at @AVIVAStadium. ⬇#LEIvNOR #JoinTheRoar pic.twitter.com/fwi9Xs5bwQ
— Leinster Rugby (@leinsterrugby) December 9, 2019

Sound a little familiar?

They were very different teams, but Chris Boyd and his Saints team will at least take some solace from that success.

Of course, winning in Dublin in Europe is not easy – no team has managed since December 2015 even if Ulster came mighty close in last season’s quarter-finals.

In fact, winning away from home after you have been beaten on your own patch is notoriously difficult.

In the past three seasons in Europe, only one team has managed it. That was Exeter Chiefs, who did so both last year against Gloucester, and two seasons previously against Bordeaux-Bègles. On neither occasion was it enough to see them through to the knockout stages.

Go back one more season and Wasps went down at home to Bath before turning the tables on their domestic rivals on their way to reaching the last eight.

That Wasps side is one of just three teams to have lost the first game of a head to head in the Champions Cup in the last decade and still make it through to the quarter-finals (the others were Saracens who lost twice to Clermont in ²⁰¹⁷⁄₁₈ and Toulouse who were upset at home before bouncing back against Connacht in ²⁰¹³⁄₁₄).

Considering all that, the prospects look bleak for the five teams beaten on home soil the weekend just gone, particularly as three of them are winless (Ospreys, La Rochelle and Bath) while another, Sale, is already eight points off the pace in their pool.

Check out the gallery from Saturday's win in Northampton: https://t.co/Ey1IZr31PL 👊📷#NORvLEI #JoinTheRoar pic.twitter.com/YYyeHF58o8
— Leinster Rugby (@leinsterrugby) December 9, 2019

So that leaves Saints. A team who lead the way in England and looked like they might trouble Leinster for a half in the East Midlands. Instead, the reigning Guinness PRO14 champions put on a show of clinical rugby with three tries in nine minutes either side of half-time to underline their status as the competition’s overwhelming favourites.

For Boyd, the big difference between the two teams was the level of physicality, and unfortunately for the former Hurricanes coach, that is one thing it is difficult to change in the space of a week.

The other gap came in execution. Leinster took almost every chance that came their way and Saints did not. That may change this week if the teams finish with similar numbers of clean breaks, defenders beaten and ruck efficiency, as they did on Saturday.

It may also require Boyd to look outside the box for ways to counter Leinster’s power.

Rugby is perhaps not as conducive to single tactical changes transforming a match-up in the way that say an NBA play-off series can flip on its head halfway through a seven-game series.

But if there is a time where coaches can really have an impact in the Xs and Os, it is now.

Those who argue that rugby is overcoached are probably right. For one weekend however, overcoaching is the name of the game.