It doesn't need to be said; you can see it in the heightened tension on their faces, sense it from their rigid body language. When players face their native province, while they may not admit it publicly, they always have a point to prove.
It brings another edge to tackles and adds heat around the breakdown. Emotions are charged to the max and that can spread like wildfire.
I saw it countless times throughout my career; whether it was when playing against Trevor Hogan, Seán Cronin, Stephen Keogh, Mike Ross or Eoin Reddan, or when facing Leinster alongside the likes of Felix Jones and Niall Ronan.
It's human nature. If someone tells you you're not good enough you'll want to prove them wrong when given the chance. Add the ultra-competitive mindset of professional rugby players into the mix and those scenarios are bound to throw up some testy, enthralling fares.
Listen to this week's Ulster Rugby Round Up podcast as we preview the game:
Munster's victory against Leinster may not have been easy on the eye at times but it was a thrilling contest that reignited the biggest rivalry in provincial rugby.
And as long as Leinster keep churning out more quality academy players than they can handle, that talent overflow will give the other three provinces - assuming they keep developing their own underage prospects and recruit cleverly - a good chance of staying in touch.
In years gone by, many more players would have opted to try their hand in England or France if their career was not progressing as they had hoped with their home province, but the magnetic pull of international rugby, and the need to ply your trade here to have realistic aspirations of wearing an Ireland shirt, is keeping the provincial larders well stocked.
Ulster have embraced the internal migration of Irish rugby; in today's 23 they have four players of Leinster stock: Nick Timoney, Alan O'Connor, Greg Jones and Dave Shanahan, while Jordi Murphy, John Cooney, Marty Moore and Eric O'Sullivan are among those being rested after a busy festive period and with two huge European outings on the horizon.
Cooney is already adored in Belfast, while Murphy and Moore could reach similar status, each having ended up there, in very different circumstances, to strengthen their international hands with a World Cup in mind.
There is a feel-good factor around Ulster again and the general consensus would be that they are in a much healthier position than this time last year.
That may well be the case in terms of the atmosphere in Belfast, but the cold reality is their results are actually a touch behind where they were at this stage last season.
Ulster are currently second in Conference B of the PRO14, 16 points behind today's opponents, having won seven, drawn one and lost four of their opening 12 games, for a total of 33 points.
At the corresponding stage of last season Ulster were travelling relatively well, with eight wins, one draw and three defeats, for a combined points total of 40.
Their Champions Cup campaigns are almost identical - although they are one bonus point better off this season - with a penultimate pool game at home against French giants (Racing 92 this year, La Rochelle 12 months ago) before finishing with a tricky assignment in England (Leicester in two weeks' time, Wasps in 2018).
Dan McFarland has made a good impression thus far, and he must also be afforded some leeway to get his ideas and systems running to his liking, but he will also be acutely aware that it was at this point last year that Ulster's season began to unravel.
They lost 38-7 to Leinster at the RDS Arena a year ago tomorrow, and while they followed that with a victory at home to La Rochelle to give themselves a chance of progressing to the last eight of the Champions Cup, they came up well short at the Ricoh Arena against Wasps a week later.
Three defeats from four PRO14 outings in February and March last year - the sole win being a home trouncing of the listless Southern Kings - ultimately ended their hopes of finishing in the top three of Conference B, their impressive late-season rally going unrewarded.
Another season without knockout rugby would be nothing short of a disaster for a club like Ulster, and with Benetton, Scarlets and Edinburgh all within three points of McFarland's side, there will likely be an almighty scrap for second and third place in Conference B over the next four months.
I played against McFarland on a number of occasions and I've since met him off the field a few times; he's a very likeable, intelligent guy who has made a promising start to life at the Kingspan.
Ulster have been building confidence - back-to-back Champions Cup wins against Scarlets sandwiched by home PRO14 victories against Cardiff and Munster - but last weekend's loss in Galway will have taken the wind out of their sails somewhat.
Travelling to Dublin with an under-strength side has the potential to further rock the Ulster boat, and I do fear for them this evening against the reigning champions who will still be fuming after their Limerick let-down.
The important thing is that Ulster, no matter how this evening's game pans out, don't let another season pass them by. They haven't played knockout rugby since a 2016 PRO12 semi-final defeat to today's opponents.
It is not just their players of Leinster stock who have a point to prove - collectively they need to stand up and lift Ulster back to where they belong.