Joe Kernan: Monaghan's knockout blow has ignited the Championship race
It was Down who first popped tricky questions to Donegal this year when they came close to unseating Jim McGuinness's side in the Ulster Championship semi-final at Kingspan Breffni Park, Cavan.
Now Monaghan have gone a stage further by not only querying the All-Ireland champions' tactical nous but probing their character and psyche.
And the revelations which have emerged are quite startling. The 'invincible' tag with which Donegal have been garlanded has slipped somewhat, their strength in depth is rather more fragile than had been perceived and their appetite will come under the closest scrutiny for the remainder of their tenure in the All-Ireland series.
Monaghan, fiercely committed in mind and body, dismantled a few myths that have surrounded this Donegal side and in doing so have to a certain extent opened up a championship race which has up until now been dominated by one word – Dublin.
I well recall Armagh losing an Ulster Championship match to Monaghan during my watch in 2003 – we were the reigning All-Ireland champions then – and our bus being pounded by excited Farney fists as it slowly made its way out of Clones.
Not a murmur was exchanged on the bus because the hurt of defeat was too palpable.
Suffice to say that the players provided their own answer by going on to reach their second successive All-Ireland final in which they were beaten by Tyrone.
Monaghan themselves have experienced this same gnawing hurt having lost the 2007 and 2010 Ulster finals to Tyrone.
Thus it was hardly surprising that the celebrations in St Tiernach's Park and over the following two days throughout the county were on a par with those that greeted Limerick's Munster championship hurling triumph the previous week-end.
Hunger is a tremendous motivational tool and Monaghan had it in spades last Sunday with some players, notably Padraig Donaghy and Darren Hughes, prepared to put their heads in places where another man might not be willing to put a shovel.
In the build-up to the Ulster final, I was asked many times to predict the outcome.
Like a lot of people, I thought that Donegal had the capacity to make it three consecutive titles.
But I qualified this by repeating over and over again – if truth be told, I got tired listening to myself saying it – that any team can be beaten on a given day.
Last Sunday was undoubtedly Monaghan's given day – indeed, it was one of their most glorious sporting triumphs.
How appropriate then that in the aftermath of a memorable match I should have been a guest of Barry McGuigan's mother in her home along with my good friend Eamonn Mackle, one of my backroom team while I was Armagh manager.
We toasted Monaghan's success in the home of one of the county's most famous sons, with his mum expressing the hope that they can perhaps provide further knock-out blows in the concluding stages of the All-Ireland series.