There is a sustainable argument that this is a golden age for football. There have been five different All-Ireland champions in as many years – fewer than in the 1992-98 period but not by much. The fact that the five of them occupy the top five positions on the betting list for this year's championship would suggest that the sequence isn't going to make it to six but it still adds up to a very competitive field.

Mayo are next in line at the bookies and the only outliers in that they have contested three All-Ireland finals in the past nine years but failed to win any of them. Dublin could be similarly categorised, albeit for a different reason: the county has appeared in just one final in the past 18 years, in 2011 when they won.

For a long time between 2003 and ‘09 there was an apprehension that the qualifier system had served to make the All-Ireland a more elitist competition than it had previously been by allowing established counties to bounce back from what had once been lethal defeats.

For all the heart-warming victories achieved by the likes of Sligo, Fermanagh and Wexford at the interim level of championship football the summit of achievement was confined to very few, in the years in question just two: Tyrone and Kerry.

But a quick scan of the 12 years of qualifier seasons shows that the Sam Maguire went back to seven counties, a more than respectable comparison with the previous 12 years - one of the most open in GAA history - which saw eight different counties win.

Detailing the prospects of counties over the coming four months is difficult because it requires a combination of data and unknown influences, more about which later, but one gauge that has become reliable is league performance.

In the past 12 years there have been five doubles of league and championship, two All-Irelands won by counties beaten in the previous spring’s league final and a further two occasion son which the defeated league finalists have reached the September final.

In short, the league final has had a direct relevance to the All-Ireland final in all but three seasons since the qualifiers were introduced.

Is this because the serious teams treat it seriously or because progress in the league has beneficial effects?

The latter appears more likely because since the championship has become extended and the football season moved a calendar-year basis, sustained performance has become more important. An All-Ireland win these days is more the product of a long-distance run than interval sprints.

Teams practised in championship play can use that experience to make sure that they’re still standing by the August holiday but it’s a fair bet that any team achieving a breakthrough All-Ireland will have developed during the league.

Still there are complications. This year Donegal became the first county of the qualifier era to get relegated as All-Ireland champions. This is both a challenge to them and the established was of doing things.

It’s safe to say that any impact is unlikely to be felt this year: the cumulative lessons of the spring had been well learned for better or worse by the time Paul Mannion’s injury-time equaliser for Dublin condemned Donegal to Division Two in the dying seconds of the regulation league campaign.

Otherwise the champions’ league hasn’t been significantly different to last year’s.

There’s another anomaly in Donegal’s emergence, which makes them different to their predecessors. They didn’t encounter a championship crisis on the way to winning their All-Ireland. Most of the teams who have lifted Sam Maguire since 2001 have had to gaze into the abyss at some stage of the season - half of them after provincial defeats - and resolve that crisis.

What doesn't kill you makes you stronger. Galway (2001), Tyrone (2005) and Kerry (2006) all took the lessons of defeat and used them to re-arrange the teams to spectacular effect.

Even for teams coming through the provinces, there have been crisis moments. Tyrone in 2003 had to scramble to draw the Ulster final against Down, the success of whose aerial bombardment prompted Mickey Harte to redeploy the late Cormac McAnallen to full back, a move which completed the configuration that would win the county's first All-Ireland.

A year later, Kerry needed Darragh Ó Sé to pull down a ball at his own crossbar in order to prevent Limerick taking the Munster title in the drawn provincial final.

Dublin two years ago stared defeat in the face in three of their last four matches, including the All-Ireland final but recovered to survive and thrive.

Last year Donegal nearly conceded a goal against Tyrone, which would have annulled their clear superiority in the match but Paul Durcan’s save prevented a replay not defeat and there’s little to suggest the champions wouldn’t have negotiated the replay.

Who knows what incidents and accidents await the main contenders in the weeks ahead?

Only one county has retained the All-Ireland in the past 22 years and Kerry had the advantage of a managerial succession to refresh things between 2006 and ‘07 as well as an outstanding team.

Are Donegal ready to emulate them? They have the disadvantage of having to open at full throttle against Tyrone, which will make for a long, long season.

A third successive year without any significant additions to the match-day panel increases the pressure and although it’s hard not to see them lining up in August it will be equally hard for them to avoid the ebbing of the willpower that has undone most previous champions.

Kerry and Cork both tussled mightily with Donegal last year but although they have deep reserves of championship craft neither have been able to strengthen their playing lists to what you suspect is the necessary level and Cork have also lost one the game's great young attacking talents Colm O'Neill to the cruciate curse.

Mayo come under the same heading in that they needed during the league to uncover a shooter capable of giving additional poke to a hard working attack. Instead they are beset by further ill-fortune.

Although Cillian O'Connor has become one of the steadiest dead-ball converters in the game, Andy Moran is still battling to overcome his cruciate injury, picked up last August and Michael Conroy picked up an eve-of-championship injury to join a number of others in the treatment room.

Mayo continue to be dangerous opponents for any team not bringing it’s a game to the contest but without an injection of fresh blood, can they step up?

The one thing that separates Dublin and Tyrone from the other contenders at present is that they have brought through a number of young players and gone the distance in the league.

Harte’s best summer teams have always been happiest doing well in the spring and Tyrone’s best championship in five years is on the cards.

Dublin are favourites for the Sam Maguire, a reflection of money staked, obviously, but also of the most impressive league campaign of any of the contenders and a first title in 20 years. Rory O’Carroll still has to return and will go some way to locking down an at times hospitable defence.

Alan Brogan’s hoped-for recovery from a long-term injury is likely to be more critical as the year wears on and consistent attacking strategies become a strict requirement.

Early-season exchanges are appetising. The coming fortnight sees Galway and Mayo followed by Donegal and Tyrone. These have a perhaps unappreciated significance in that no team who loses in May has gone on to win an All-Ireland and only one - Armagh 10 years ago - has even reached the final.

Let’s play.