Gaelic Games: Everything you know is wrong. Perhaps the sun is at the centre of the Solar System but Copernicus was never in Clones. At least not on championship Sundays.

Yesterday the All-Ireland champions were felled by a forgotten county and today the venerable old competition looks all the more open.

Games like these are the reason people love the championship. How is it that Monaghan, with a summer record that reads like a lovelorn verse from Kavanagh, could suddenly come to boss the All-Ireland champions? All year they have been building to these 70 minutes and oh, how they realised them. 0-13 to 0-9 is an ordinary score line, but this was no ordinary day.

"People thought we were just going out to keep the score down," noted Paul Finlay, one of the heroes of the hour and a young man whose name is redolent of Monaghan's last truly distinguished era in the game.

"But you know, inside our camp we had this quiet feeling that we would beat Armagh."

In a way, it was a very un-Ulster coup. Perhaps that is because its architect hails from the Royal County. Colm Coyle is a stranger in these parts but already he has carved out a bit of local history for himself. His apprenticeship under Sean Boylan appears to have paid off.

Yesterday, bespectacled and studious on the sideline, he displayed a sense of calm and manifest destiny that transferred itself to his young players. Coyle Meathified the Ulster county. No reputation was too big, no cause too small. Armagh were as big as they come, a fact that just awakens the sense of smell in any self-regarding Meath man. Armagh were the summit.

"I like mountains," he smiled afterwards, puffing on a smoke and deliberating on the finest hour of his young life in management.

"This is up there. I suppose I like a challenge like that when people are knocking you and you are up against serious odds. I know a few people down in Meath who made a lot of money on this. This was a tough day for Armagh. I think when you are All-Ireland champions, your first day out is always the hardest."

For Armagh, it looked right but felt wrong. The orange was as bright as ever but they lacked the fizz. Big Joe Kernan may well have felt this day coming in his bones. He stood quietly in the rain watching as the day stripped his team bare. Great players do not simply disappear, but in Clones, Joe scanned the field in vain.

"Our lads are hurting in that dressing-room now and I am glad they are because we didn't perform out there. Ah, you talk about the bit of hatred and the bit of revenge - we just didn't have it. Monaghan and ourselves are good rivals and that is it. You hear talk about the famous Ulster title and nobody defending it, but until you experience it, you can't feel it. I would like to think that if the two teams meet again, there will be more bite to us."

As games go, this will be bettered. Monaghan were more streetwise than they had a right to be, with old soldiers like Jason Hughes pointing the way for the younger guns like Raymond Ronaghan and Finlay, who finished his first championship afternoon with eight points. Even when Damian Freeman was presented with his second yellow after 45 minutes, Monaghan didn't flinch.

"Well, we had prepared for the scenario where either Armagh or ourselves would lose a man," said Coyle. "When that happened, it was just a question of getting on with it."

Up 0-6 to 0-4, they never trailed throughout a long and gripping second half. Armagh hung on, but with Kieran McGeeney gazing on from the stands, they could not summon the unnameable quality that captured the imagination last year.

"Look, that wasn't the true Armagh out there. I think you all know that," said Joe before departing. And that may be so. But as Monaghan danced off in the rain, all that was held as true had been wiped clean.