Just when they thought they had dealt with one northern nemesis, another has emerged to spook a weary Kingdom.
Donegal and Kerry will probably never develop into the same long-distance rivalry, however, that has framed Tyrone and and the Kingdom for the last decade, because Kerry won't have the resources or, perhaps even the will, to chase this one down.
Two weeks on from the therapy of a championship victory over Tyrone, that result can now be seen for what it was, a nod to the past, not a means to a more vibrant future.
Ultimately, Donegal outfought, outthought and outran Kerry in their first ever championship meeting, just as they had privately felt they could do.
A two-point margin of victory at the end didn't do justice to their dominance, their ability to control the game for long patches.
Credit Kerry for the manner of their comeback over the last seven minutes, as they rescued a perilous situation and restored some respectability.
But it was small consolation on an afternoon where, if the music hasn't died completely, then it has become barely audible for this team. It won't be the same again for them.
Donegal had surged into a 1-11 to
0-8 lead when Colm McFadden pointed a free on 64 minutes. But Kerry got the opening they craved, Donnacha Walsh teeing up Kieran Donaghy to bat home a goal at close range.
Rory Kavanagh, a hugely industrious presence throughout, took possession from a Donegal kick-out and fed Karl Lacey on the burst. With Kerry numbers committed to attack, Lacey surged clear and popped an insurance point to close the deal.
That Lacey should be so full of running in the 71st minute of a game of such intensity is testament to the staying power of this Donegal team. He was immense throughout that second half.
They will be hard to stop, even for a team as talented and as powerful as Cork.
The growing confidence Donegal have in the game plan they have committed to over the last 19 months is reflected in the greater numbers they now commit to attack.
Their style may not please every eye, but you can't argue with the quality of their last score before half-time, started by Mark McHugh in the shadow of his own goalposts and finished within seconds at the other end by Leo McLoone.
The pace and endurance required for the sequence of transfers was most impressive.
McHugh is now Donegal's pivotal player, the man whose role has now done most to develop their game from 2011.
He worked well as a sweeper around the McGee brothers, who were tasked with minding Donaghy and Colm Cooper, but it was the young Kilcar man's playmaking from those deep positions that really stood out.
It was an attritional day for Kerry. Eoin Brosnan limped out of the action after only 24 minutes, Bryan Sheehan was struggling before half-time with an injury and played on until the 45th minute when he had to depart. He was joined by Declan O'Sullivan in a double substitution that had to have lifted Donegal.
O'Sullivan, Jack O'Connor explained afterwards, had run out of steam at that point and Jack knows his club colleague better than most.
But it was still a curious substitution. With the high ball into Donaghy not reaping any real dividend, would it not have been better to station him closer to goals for a spell and possibly release Cooper?
But losing Sheehan and calling in O'Sullivan was a pivotal moment of the game, a time when you sensed options were quickly running out for Kerry and that belief would subsequently drain from them. It was one scrap too many.
At that point Donegal led by 1-6 to 0-7. They won the next 20 minute period by 0-5 to 0-1 before Donaghy got the goal and, if this game has a snapshot, it was the manner in which Frank McGlynn got down to block Galvin to concede a '45', which was subsequently missed.
It had been billed as a game that would 'fascinate' more than entertain and that's how it panned out.
A cynical first half, laced with so many deliberate fouls that killed momentum on both sides, gave way to a more free-flowing third quarter as Donegal sought to build on a 1-4 to 0-5 interval lead.
Both sides committed big numbers to defence when they didn't have possession, with Kerry regularly deploying up to 11 players inside their own half to screen Donegal's strike runners.
It led to very few goal chances and, indeed, it required something freakish for Donegal to establish control through a Colm McFadden goal.
His sixth-minute sideline deceived Brendan Kealy, who had the distraction of Aidan O'Mahony and Michael Murphy wrestling each other in front of him, and it provided an advantage, 1-1 to 0-1, which Donegal didn't subsequently relinquish.
In what was inevitably going to be a low scoring affair it was a very significant break.
Donegal had some exceptional defensive performances, none more so than from Paddy McGrath, but the drivers were McHugh, Ryan Bradley, Paddy McBrearty, Kavanagh and Lacey, who repeatedly broke tackles and overlapped to eventually squeeze their illustrious opponents into near submission.
The polish of McFadden's finishing was the last critical element as he added to what had already been his best-ever season in a long Donegal career.
From an early stage, it was clear that space would be at a premium for Kerry's gifted forwards.
Cooper got clear on one occasion just before the break. He linked with Donaghy and had goal clearly on his mind, but, in the end, had to settle for a fisted point in added time at the end of the first half and that was as close as he got.
It is a wonderful coaching achievement for Jim McGuinness to have taken this team to a second successive All-Ireland semi-final, courtesy of back-to-back Ulster titles.
That a player like Michael Murphy is willing to sacrifice the finer points of his game to contribute to the communal effort underlines the journey they are on.
In the cold light of day, however, they will realise that they have beaten a Kerry team for whom the light is fading fast.
Scorers -- Donegal: C McFadden 1-6 (1-0 s-l, 0-2f), M Murphy 0-3 (2f), C Toye, L McLoone, K Lacey all 0-1 each. Kerry: C Cooper 0-4 (2f), K Donaghy 1-0, A Maher 0-2, B Sheehan (f), P Galvin, Declan O'Sullivan, J O'Donoghue all 0-1 each.
Donegal -- P Durcan; 7; E McGee 6, N McGee 7, P McGrath 7; F McGlynn 7, K Lacey 8, A Thompson 6; McMcElhinney 5 , R Kavanagh 8; P McBrearty 7, M McHugh 8, R Bradley 7; C McFadden 8, M Murphy 7, L McLoone 6. Subs: N Gallagher for McElhinney (h-t), David Walsh for Bradley (59), D McLoughlin for McBrearty (71).
Kerry -- B Kealy 5; M O Se 6, A O'Mahony 7, S Enright 6; T O Se 8, E Brosnan 5, K Young 5; A Maher 7, B Sheehan 5; P Galvin 6, Declan O'Sullivan 5, D Walsh 7; J O'Donoghue 5, C Cooper 7, K Donaghy 6. Subs: B McGuire 6 for Brosnan (24), Darran O'Sullivan 6 for Young (32), J Buckley 5 for Sheehan (45), K O'Leary 4 for Declan O'Sullivan (45), P Curtin 4 for O'Donoghue (45).
Ref -- Marty Duffy (Sligo)