In a world that revolves around human nature, and therefore human error, opponents develop habits that offer the hope of likely advantage. Some counter this with subterfuge; others offer no disguise whatsoever.
Northampton appear to exist by the principle that, even if everyone they play knows exactly what's coming, they will do it so well – with such conviction – that it will take some stopping. Saints' game has, for a few seasons now, been all about momentum. For a side who need to be on the front foot to truly thrive, two areas are crucial to their hopes of victory today. And so these facets of the game become the most vital for Saracens to defend.
Since Soane Tonga'uiha switched from tighthead to loosehead and Brian Mujati took position on the right, Saints' scrum has been both an effective generator of penalties and a constant supplier of forward momentum.
As they force opposing packs into reverse, so the defending back-line rocks back on to its heels. Then Saints' midfield can begin to punch the holes that allow the pack to get around the corner and carry hard, while opposing forwards are effectively having to run back around a breakdown to get where they need to be to defend.
James Downey was crucial to this plan before he left for Munster. A massive unit who carried with evil intent, he was arguably the pivotal player in that team. The midfield of Dom Waldouck and George Pisi is replete with tenacity and raw ability, but the crushing power of the Downey era has gone.
Waldouck is a very underrated player, with a low error-count and a punchy strength that belies his relatively diminutive stature. But it is outside him that I think the key confrontation will take place. Pisi, a wonderful attacking centre with balance, vision, pace and, above all, the confidence to have a crack, will come up against possibly the world's best defensive centre. If you run straight into Manu Tuilagi he will do you more damage, but if an attack needs reading and shutting down, Brad Barritt is world-class.
Pisi is one of those players that every supporter wants in their team. He has the sort of talent that even leaves his team mates guessing at times. Often their job is just to back Pisi to beat a man, make ground and free up the ball, and react accordingly. Barritt's job is, where possible, to close down his space and hammer him before he has the chance to do what he does. This will be incredibly interesting to watch as, in real terms, these are two completely different players wearing the same number.
Barritt showed against the All Blacks last autumn that he does possess enough pace to cause problems in attack and sufficient lightness of touch to move the ball when the window opens. But he remains primarily a cultured slugger. Today he faces a huge test and, while he seeks to line up the Samoan and knock the wind out of him, Pisi will look to leave the committed brute flailing as he dances by with poise and agility.
Sarries will know exactly what is coming. Saints will arrive with a big, aggressive scrum that will do its best to extract penalties and points. Their tighthead (be it Mujati, Tom Mercey or Doran Jones) will work a dubious angle (unless straightened up by the referee) designed to pressure the opposing hooker and allow Tonga'uiha to work almost outside Matt Stevens as Dylan Hartley attacks him head on.
This attempted sheering on the angle can be very hard to counter, but the frankness with which Saints state their intentions on a weekly basis means that the Sarries pack will have a plan. If they can execute it, Saints' dreams of midfield momentum will be far harder to realise. But in Pisi they have a man who can create momentum and release his side from anywhere. This flash of brilliance is always in him.
England's anchorman will either quietly enhance his reputation again or fall victim to one of the Premiership's most gifted individuals. A key battle within a war, and I can't wait.