Kick-out conundrum adds to the intrigue over D-Day in Castlebar
There are so many levels of intrigue to the biggest game yet in the short history of the Super 8s.
Donegal's form; Mayo's struggle to find theirs for longer than those short but electrifying flourishes. The readiness of James Horan's injured aces for do-or-die battle in Castlebar tomorrow. Mayo's incredible endurance, forever fighting against the dying of the light.
Who can stop Michael Murphy - and his telepathic partner, Ryan McHugh? Will Stephen Rochford's forensic knowledge of this Mayo group prove the tactical trump card for Donegal?
And then you've the kick-outs.
Shaun Patton's restarts have been the subject of endless summer praise. Little wonder, given the length and trajectory and statistical success of the Donegal 'keeper's distribution off the tee - many to the wings, favouring a teammate, frequently his ever-roaming skipper, Murphy.
When Patton goes long (as he did in that moment of pivotal parity against Meath, when Murphy flicked on majestically to a sprinting McHugh to create a goal chance that Jamie Brennan pointed) he can hit the opposing half-back line and turn defence into attack within seconds.
When a 'keeper has that weapon in his holster, he can "create very dangerous situations with the minimum of effort," says Martin Carney, who enjoyed a lengthy career with his native Donegal and adopted Mayo.
David Clarke, we all know, lacks the prodigious range of his Donegal counterpart.
In every other respect, the 35-year-old has long been among the game's leading No 1s. Here is a back-to-back All Star (controversially, but that's a long story) whose shot-stopping has been a game-saver on countless occasions; who excels in his judgement and command of the airspace around the Mayo goalmouth.
But his restarts, especially the longer ones that tend to hang in the air, have long attracted debate - among the media and also management teams, rival ones and closer to home.
Rochford was the Mayo boss who oversaw the decision to replace Clarke with Rob Hennelly for the 2016 All-Ireland final replay against Dublin, with disastrous consequences.
More recently, Hennelly was No 1 for the triumphant end of Mayo's league campaign (in late March) and their inglorious Connacht exit to Roscommon (in May) when an intercepted short kick-out led directly to a goal.
Duly restored, Clarke has started the last five games. But for their Super 8s opener in Killarney last month, Kerry went after the Mayo kick-out with a zonal press that reaped spectacular first half success - maybe it's no coincidence that Donie Buckley, so long part of the Mayo brains trust, is now back with his native Kerry.
"There is no doubt about it: in the last couple of games, teams appear to have worked harder on David Clarke's kick-outs than they had in the past. I thought he was rumbled in Killarney," reckons Carney.
Blame is a two-way street. Carney surmises that a lot of his long kick-outs "aren't carrying far enough to reach Aidan O'Shea. I don't think the link with Aidan O'Shea is what it should be."
But he reckons it's "a little bit unfair" to lump it all on Clarke's head, especially given the dearth of movement against Kerry when Mayo targets were "far too static at times".
There has been speculation this week that Horan may switch goalkeepers again. This line of thinking is predicated on the belief that Hennelly's kick-out range offers Mayo a better chance of achieving the front-foot possession they'll need to stay alive tomorrow - especially as they may struggle to get much joy from Patton.
Carney is unsure who will get the nod: he rates both Mayo options as outstanding 'keepers who are stronger in different areas. But Hennelly isn't all about what he offers with the boot: the pundit struggles to recall "a display of goalkeeping that surpassed" Hennelly's shot-stopping heroics against Dublin in Croke Park last February.
He concludes: "The criticism Hennelly has shipped in the past is completely disproportionate to a lot of the errors he has made … I just think the public here have a thing about Robert Hennelly in goals. That one error in the replay of the 2016 final has stuck to him for far too long."