The smart boys won. Smirking away down the back of the class, homework done to the last full stop. Donegal, the biggest underdogs in an All-Ireland semi-final for 20 years, skipped away to the hills last night cackling at a raid for the ages. In front of 81,500 sets of eyes, they left Dublin looking like an old sweater turned inside out, its edges frayed and its patterns fuzzy.

Nobody does it better. Nobody takes quite such delight in turning the best players in the land into the one thing they don't want to be – panicked footballers making split-second decisions with the whole country watching. The Dublin that had eased its way through Leinster and had squashed Monaghan like a bug in the quarter-final, that Dublin got fed into the chipper here and came out the other side as dust. Only Donegal could have done that to them.

Attacking play

The final score was 3-14 to 0-17. That's a scoreline worth rummaging through for a moment or two to see what peculiarities we can unearth. This was Dublin's 11th championship game under Jim Gavin – 0-17 is the least they've scored under him, 3-14 is the most they've conceded. Never before have they not scored a goal. At no stage this summer before have they gone 10 minutes in any game without putting at least a point on the board. Here, it happened twice, once in either half.

If it has always been suspected that Gavin’s devotion to attacking play could one day end up with a gaudy total being run up against them, there were very few predicting that this would be the team to do it. Yet it’s the destructive beauty of Donegal’s expertise that will linger here. Time and again they cocked an eye at the looming edifice of Dublin’s full-court press and scanned it for a side door. As soon as they found one, they made it count.

“It was a challenge,” said Jim McGuinness afterwards.

“The reality for us was, could we face it down? When you want to beat Dublin you have to face that challenge down. If you don’t face that challenge down or you take a backward step – one backward step – they will absolutely annihilate you.

“The big thing was to keep doing what we spoke about, keep driving the game plan, keep driving themselves to the 70th minute and believe in themselves. I asked them, ‘Do you believe in yourself and do you believe in your team-mates?’ That was the key thing. They kept pushing and pushing and we got over the line.”

Yet for the longest time in the first half, this was a game that bore out all we'd said in the build-up. Donegal packed their defence, Dublin pushed up on them. For most of Paul Durcan's kick-outs, only Colm McFadden, Mick Fitzsimons and Stephen Cluxton stayed in the Dublin half of the pitch. Every other Dub was advanced. It was like they attached electrodes to every vital organ Donegal had.

And for 25 minutes, it worked a dream. Dublin kicked points from all distances and angles, worked the positions and took the scores. Paul Flynn purred his way to four first-half points, Diarmuid Connolly speared three of his own. Dublin led by 0-9 to 0-4 after his third and we all presumed we knew how this would shake out. Dublin would take a goal chance or two and that would be that.

Donegal are different though. We generally talk of miles on the clock in the pejorative, forgetting that you see some stuff as you rack up those miles. They didn’t win an All-Ireland by getting an attack of the vapours any time a team got on a roll and they weren’t in the mood to now.

Conceded

Michael Murphy and Neil Gallagher put their hands up and won a few kick-outs, Odhrán MacNiallais and the exceptional Ryan McHugh pushed on for scores. They kicked 1-4 on the bounce to forge a lead – again, the first time all summer that Dublin have conceded a run so heavily.

“We weren’t surprised,” shrugged Eamonn McGee. “We knew if we got goals that we would come out the right side of the result. So it was no big shock, like . . I knew going down the home stretch with the crowd of boys behind here that if we kept at it, these boys would pull it out of the bag.

“It was a bit like Ali in the Foreman fight – absorb everything and try and stay in there. It was a big psychological blow for the Dubs to throw everything at us and to find themselves a point down.”

The lead was pushed out to four soon after the restart when McHugh got in for his second goal. And the more Dublin pushed on, the better Donegal exploited the space in behind. A full-court press works if you win the ball; if you don’t, you better have left someone back sweeping just in case. Dublin missed Ger Brennan yesterday, never more than for Donegal’s third goal when all it took was a Murphy flick in midfield to open up their whole defence.

So Donegal ride on, the prospect of a final against Kerry in their saddlebag. For the rest of us, rarely has the gruel of being wrong felt as nourishing.