Given Dessie Farrell's relative unfamiliarity with this current bunch of players at the start of his year, it stands to reason that he may have learned more about them in Navan a couple of weeks back than in the rest of his reign combined.
With three minutes to go until half-time that afternoon, Dublin trailed 0-9 to 0-2.
They trailed a team many of whom had been hammered by at minor championship level in a match they generally weren't fancied to win.
Yet they forced extra-time through nothing more complex than a defensive rejig, honest, determined work and the strikingly accurate finishing of Con O'Callaghan.
To there, they hadn't experienced that form of hardship as a group - certainly not since Farrell assumed command - so their ability to think, fight and play their way back out of it can only have pleased him and re-emphasised their collective credentials.
Afterwards, Farrell accepted that his squad wasn't the one most bursting at the seams with individual talent but together, he has turned them into a potent bunch.
No question, O'Callaghan is - and has been so far this year - a beacon for this Dublin under-21 team and if competition is tight just now in his position with the seniors, it's worth repeating that the younger O'Callaghan brother is eligible for the grade again next year.
He kicked 1-7 against Meath, 0-5 against Laois in the Leinster semi-final and another 1-7 in Navan that afternoon and if he is the brightest star of this team, the rest of the constellation align in just the right patterns behind him.
In this, Farrell has created a well-drilled team, one for whom strong support play and disciplined tackling are as vital as O'Callaghan's scoring exploits.
It stands to reason, too.
In Farrell's first year as U21 manager in 2013, a team dripping with luxurious talent fell in the rain to Longford in Parnell Park.
A year later, a more robust side waltzed to the All-Ireland.
Even Farrell's two years as Dublin minor manager hint at the same conclusion.
Of the 2012 team that won the All-Ireland title, only Cormac Costello, Eric Lowndes, David Byrne and Shane Carthy have had any penetration at senior level since their ascension.
The team of a year previous; the one that lost to Tipperary in the final, was bejewelled by the presence of Jack McCaffrey, Ciarán Kilkenny, Paul Mannion, John Small and Emmett Ó Conghaile - as well as Costello, Lowndes and Byrne.
No doubt that Kildare will squeeze more seniors out of their team than Dublin will from theirs and that's not solely representative of the competition they face.
Certainly, Ben McCormack and Neil Flynn will be sought after now by Cian O'Neill, having kicked nine points from play - 15 in total - against a previously rigid and snarly Dublin defence but that merely made the process of quietening those two whilst chipping into Kildare's lead all the more impressive when it did come to pass.
Shane Clayton added some pace and ingenuity to the Dublin defence when he came in and if Colm Basquel wasn't nearly as emphatic in his contribution as he was off the bench against Laois a round previously, both Ballyboden St Enda's players should have benefited from another couple of weeks devoted exclusively to county duties.
Similarly, this Mayo team have pedigree.
Many of them hold the distinction of winning an All-Ireland minor title in 2013 which in a county like Mayo, shoves a whole pile more expectation on their shoulders.
During the week, Aidan O'Shea called Diarmuid O'Connor a "freak". Certainly, he is of the prolific variety of wing-forward (though he plays in midfield for the U21s) and puts in the effort between the '45s' to back it up.
Against Roscommon - their first Connacht U21 final in seven years - Mayo's wing-forwards, Fergal Boland and Michael Plunkett - dropped deep into their own half and in Stephen Coen, they have a player wholly capable of organising a defence. They also - like Dublin - came back from behind against a team fancied to win, though that minor win gives them an edge.
This Dublin team have just delivered a third Leinster U21 title on the spin for the county. They're a neat unit with the right blend of pace at the back, graft in the middle and a couple of gems up front.
They've also responded impressively to being well down in a match they were supposed to lose.
Ergo, in as much as any underage team can be trusted to follow a line of form, Dublin should keep it straight through to the final.
Odds: Dublin EVS, Draw 15/2, Mayo EVS
All-Ireland u21FC semi-final: Dublin v Mayo, Tullamore, today (2.45, live tg4)