All-Ireland Senior Football Championship quarter-final: Donegal v Mayo (Tonight, Croke Park, 6pm)
Click here to follow our live blog from Croke Park
In 2012, Donegal were Gaelic football’s 'Invincibles'. Their defence was virtually impenetrable, their counter-attack utterly devastating.
Since that perfect summer they have had to deal with a familiar charge: that they have often looked leggy in games, that the lung power isn't quite what it used to be.
Everything they do for the remainder of their careers will be compared to 2012.
Of course, it's highly unlikely Donegal will ever scale those dizzy heights again.
And yet, while there has been inevitable slippage in the seasons that followed, Donegal have played in three Ulster finals and were the width of a post away from pushing Kerry to an All-Ireland final replay last September.
Despite the constant charges of tiredness Donegal are still a force to be reckoned with.
If they beat Mayo this evening's All-Ireland quarter-final, there is no reason why they can't reach their third All-Ireland final in four years.
After losing last month's Ulster final by a point to Monaghan, Rory Gallagher was clearly irked by reporters who enquired about the demanding Championship schedule Donegal faced and whether or not it had taken its toll on some players.
Earlier in the year, Eamonn McGee praised Gallagher for the way in which he'd tailored training for some of the older players.
“Going to training over the last four years, it was a mental battle – not in a really negative way - but you knew you were going to be absolutely dogged," said the Gweedore man, who is an injury doubt for this evening's clash.
“Okay, there’s been tough training this year, but it’s been managed so well, and you’re not really going to the well. Rory kinda looks at the individual and he knows there are certain lads in a particular age bracket that need to be managed."
Two years ago, Donegal were the proverbial dead men walking heading into Croke Park to face Mayo.
They looked tired and sluggish eight days earlier in a bruising Round Four Qualifier with Laois in Carrick-on-Shannon. Mayo duly blitzed them in the quarter-finals.
Fast-forward to the present and Frank McGlynn insists having a 13-day gap - rather than the six days they were afforded in 2013 after losing a provincial final - has made all the difference this year.
“Having the 13 days break is immense," he said. "You have that second week of training under your belt and it helps to have a couple of blow-outs in between games rather than just recovering for the full week.
“[In that instance] You’re 20 minutes into the game before you’ve got it our of your system.”
Galway was the ideal test for Donegal last weekend. The Tribesmen never quite had the tools to take them down.
Had they been facing Mayo last weekend - and not Galway - Donegal would have been out of the Championship by now.
Donegal didn’t muster a score between the 16th and 44th minutes last Saturday night. An elite team like Mayo would have won the game during Donegal's scoreless period.
Tonight will be Donegal's sixth Championship outing of the season. They have been well road-tested. It will only be Mayo's third Championship appearance.
However, the gap between Connacht title success and the All-Ireland quarter-final stages hasn't hindered Mayo in recent times as they have won all of their All-Ireland quarter-final matches in the last four seasons.
While Rory Gallagher has keenly avoided any notion of tiredness in Donegal's ranks, injuries have taken their toll.
Karl Lacey (knee) and Eamonn McGee (ankle) are doubtful starters at Croke Park tonight.
Michael Murphy has been niggled by a knee problem, while work commitments in London this year has hindered Anthony Thompson's participation.
Mayo look the fresher of the two sides. But Donegal have more intelligent footballers than the Connacht champions.
While Aidan O’Shea’s performances at full-forward this year have been rightly hailed, Donegal still attack better than Mayo.
There remains more structure and cohesion about Donegal in the final third of the field.
Colm McFadden, Michael Murphy and Patrick McBrearty can find each other with their eyes closed.
Neil Gallagher and Odhran MacNaillais's vision means that the defence-breaking runner from deep will invariably be found.
And Ryan McHugh’s brilliantly timed runs into opposition territory after primary possession has been won is one of the many sumptuous features of Donegal’s attacking play.
But here’s the catch: Donegal’s once-legendary defence is just like any other these days. Opposition forwards are no longer overcome by claustrophobia.
Rory Gallagher’s half-back line plays noticeably higher than Jim McGuinness’s ever did.
As a consequence, Gallagher’s Donegal attack better while McGuinness’s Donegal defended better.
The dislocation of defensive lines leaves the Donegal full-back line more exposed and, as Galway showed on numerous occasions, you get more scoring chances against them.
McGuinness was immovably pragmatic in how he viewed modern-day defending, while there is more of an idealist in Gallagher.
That said, Mayo can hardly be described as disciples of Catenaccio. After winning a Mayo kick-out in their Connacht semi-final, Galway’s Gary Sice only had to side-step one challenge (from Tom Parsons) to raise a green flag, albeit a game that Mayo were always in control of.
That’s why it’s hard to escape the conclusion that this All-Ireland quarter-final will be a high-scoring, entertaining, tight affair at headquarters.
Indeed, it could be a battle between Mayo's athleticism and Donegal's game intelligence.
Mayo are in good shape entering Croke Park. They have the right amount of worker bees, a more balanced midfield and a rejuvenated inside line.
Donegal are the more cerebral side but there are perhaps too many question marks hanging over them.
How fit can Lacey, McGee and Thompson be? The long scoreless periods in games. The emerging holes in defence. The legs.
This game is intriguing on every level. Mayo by two.
