A young Marty O'Reilly once wore both a Mayo and Donegal jersey to Croke Park so he could support both teams at an All-Ireland quarter-final double-header back in 2002, but all his focus will be on reaching a league final when the Tír Chonaill men pitch up in Castlebar this weekend.
There's plenty at stake for both sides. A win for Donegal could put them straight into the decider while Mayo are also desperate for the two points to usher away the possibility of relegation that looms over them this weekend.
The fixture puts O'Reilly in an unusual position. With a father from Belmullet and Billy Joe Padden as a cousin, he has always followed Mayo's football fortunes.
"When I was growing up I always had a Mayo jersey," O'Reilly recalls.
"I remember Donegal and Mayo played in a quarter-final out here (in Croke Park) one day. I had the Donegal jersey over the Mayo jersey, I pulled it off afterwards! So I was always a big Mayo supporter growing up."
Donegal will finish the league with one of the more impressive report cards. Despite the overhaul in personnel that saw them lose several experienced players and more of the 2012 All-Ireland-winning team move on, the Ballybofey native isn't surprised at how well some of the county's new faces have acquitted themselves in Division 1.
And he admitted reaching a league final was a goal from early in the campaign.
"When we met in November we knew eight or nine players weren't coming back and we have been working since then towards the league. So it didn't come as a surprise so when a lot of the players announced maybe in January or February that they weren't coming back - we had three months' training (done) at that stage," O'Reilly explains.
"When we did sit down we wanted to try and get to the league final, that was our target. We still have a chance on Sunday but Mayo will have a lot to say about that too."
A draw with dominant Dublin and wins over a previously unbeaten Tyrone have made the rest sit up and take notice as some new faces have taken centre stage. And he admits the calibre of young Donegal footballer emerging from their underage system has improved greatly
"I was talking to a friend from home about that and we thought that the Donegal minor teams and U-21s have been getting to Ulster finals and All-Ireland finals. The U-21s have been in the last four or five finals and that can only bode well.
"And it gives the younger lads huge experience going into the National League. Before that, unfortunately for our minor side we were beaten in the first round, and we were coming into a senior side with very little experience but now lads have played in front of 80,000 on All-Ireland final day.
"If you look at Karl Lacey, Michael Murphy and Ryan McHugh, even the younger lads there that have huge experience, the likes of Martin McElhinney coming back in after an injury. Mark Anthony McGinley has played the last two years, so there is a good lot of experience in the side at the minute.
Experience "Although I have to admit, we have lost a lot of experience in the last six months and since the last campaign, there's still plenty experience there too."
Having hurled for Donegal earlier in his career, O'Reilly has been a regular in the side under Rory Gallagher for the past two seasons as the Fermanagh native has looked to put more pace in the side.
"There certainly is (more pace in the team), the likes of Cian Mulligan, Eoin McHugh, Eoin Bán Gallagher. The way football has evolved a lot of the top players have a lot of pace and power. That's something we have been working on the last while to get speed into the legs and hopefully it'll pay off."
O'Reilly is one of 12 of the Donegal panel based in Dublin. A teacher in Castleknock in the same school as Cavan forward Dara McVeety, O'Reilly is keen to earn a league final place, even if it means they could face the daunting task of taking on Dublin in Croke Park, should the champions do enough in Clones against Monaghan.
"Any time you get to Croke Park and play Dublin, even if it's for the experience for the younger lads, you go out and play football; we'll go out and try and beat them.
"It was a tough game in Ballybofey, a draw in the end, but if we happen to get past Mayo on Sunday, we'll be looking forward to a league final no matter who it is against."