Ulster Final: Once again in Ulster the forces of light and dark converge. Among the more intriguing subplots in championship football has been Donegal's relentless and, to date, ill-fated obsession with toppling Armagh.

The broad fact of the relationship is that Armagh have used Donegal to redefine the best of their winning instinct, but the deeper truth is that the two counties have become locked into a fascinating and quite antagonistic rivalry that has produced many moments of controversy.

The most explicit of those occurred in Clones last June when Armagh, predictably, ran riot against a young Donegal team that lost its cool. It marked a turbulent exit from the championship for Brian McEniff, who almost managed to produce a second epoch for Donegal football.

The great Bundoran man was more upset at having three players sent off than by losing the match and there was the sense afterwards that even the most composed of the Armagh senior men were shaken by the ferocity and anger they had drawn from so many Donegal men that day. Many of us watching felt that the cost to Armagh of that victory over Donegal was that they left something of the cold instinct for winning that distinguish all great champions behind on the field. That seemed borne out by their surprising implosion against Tyrone in the epic semi-final two months later.

Since then, much has changed. Brian McIver best defined the difference between the experience of these teams when he noted that Armagh are playing for three Ulster titles in a row while Donegal are playing for three championship victories in a row.

McIver's clean and admirable transformation of what seemed like a settled team has returned a refreshing bout of optimism to the malcontent north-west. The poise in the victories over Derry and Down surprised as much as the pretty football.

It seemed almost inevitable that Armagh would come through the other side of the draw and it means that this Ulster final presents the classic contrast between fearless youth and proud champion, the universal clash best captured by Muhammad Ali's heroic display of pride and know-how against the young and impatient George Foreman in the heat of Zaire back in 1974.

The boxing legend is one of the many icons that this Armagh team have drawn inspiration from down the years. And they will be aware of how rough the last years were on Ali. Through the league and their leaden progress over Monaghan and Fermanagh in the championship, the whispers have grown louder that Joe Kernan's team is, in that most damning of phrases, "past it".

That is almost certainly nonsense. We will know for sure tomorrow - if Croke Park does not rouse them, nothing will. Donegal, though, are a tricky obstacle.

In the five championship matches they played including the 2002 Ulster final, Armagh has won each, on an aggregate score of 9-62 to 3-52. And yet back come Donegal. How many times can you kill a man? Although this is largely a new-look Donegal team, 10 of the team that starts tomorrow played against Armagh in that ill-tempered meeting a year ago.

The return of Adrian Sweeney for the classy free-taker Michael Doherty, injured since the Derry game, gives the challengers flying forward unit a retrospective flavour. But the Dungloe man has delivered before in big games and his seniority could count for a lot.

Armagh have to use their charisma and weight and experience as their chief calling card here. It is probable they will seek to meet Donegal's pace and fury with the same early on and try to rattle their opposition just like they did in 2004 and 2005.

But discipline and aptitude have been the key components in McIver's team and he has managed to get youngsters like Karl Lacey, Barry Dunnion and Ciarán Bonner operating at a blistering pace.

Armagh may look to man-mark Christy Toye or Michael Hegarty, the key men in the Donegal mechanism and will rely on old blueprints for their own game, isolating Steven McDonnell for what promises to be an absorbing tussle with young Lacey. Midfield will be bruising. It will be no surprise to see a red card or two.

Expect heightened performances from the Armagh old guard of McGrane, McGeeney, McConville and McEntee. Unlike last year, Donegal may have learned enough and are fast and sufficiently arrogant to play on the same field with Armagh without getting psyched out by them. The belief here is that by late September, Armagh will have rumbled towards that long-awaited second All-Ireland.

But they will be nervous of meeting Donegal, the irrepressible county that is travelling at a rate of knots and will sooner or later come to haunt them. However, this may not be the time.

A draw is a strong possibility, but given the fortitude and make-up of this Armagh team, they have earned the right to the presumption that they can still deliver the imperious, heavyweight hour when it matters and so become the first Northern team since Down to take three Ulster championships in a row.

Armagh: P Hearty: A Mallon, F Bellew, E McNulty; A Kernan, C McKeever, P Duffy; K McGeeney, P McGrane; M O'Rourke, J McEntee, M Mackin; S McDonnell, R Clarke, O McConville.

Donegal: P Durcan; K Lacey, P Campbell, N McGee; E McGee, B Monaghan, B Dunnion; N Gallagher, B Boyle; C Toye, M Hegarty, C Bonner; R Kavanagh, C Dunne, A Sweeney.

Croke Park, Sunday, Throw-in - 2.15pm