Jim McGuinness changed the game when he took over as Donegal manager in 2011, leading the county to the Sam Maguire employing the type of style that had never been seen in Gaelic football up to that point.
Many did not like the way they played the game, but there is little doubt that it had a massive impact on the development of the sport over the following years.
Rory Gallagher played his part in that as well, with the Fermanagh native acting as McGuinness' righthand man in the Donegal setup. Between them, they masterminded the plan to turn the team into All-Ireland champions.
However, the relationship did not last too long. Gallagher would leave the Donegal setup in 2013, with a fallout with McGuinness being the reason.
The 42-year old would go on to manage Donegal, Fermanagh, and Derry since then. He has now spoken openly about how his relationship with McGuinness went sour.
Speaking on BBC's The GAA Social, Rory Gallagher said that it was some irreconcilable differences over player selection that ultimately led to his departure.
Hand on heart, there were a few issues coming up to the Ulster final 2012. There was a few disagreements about players.
I probably don't want to go into it because it's unfair to the players that were there. I rated some players differently than [McGuinness] rated them. He had players he wanted to play that I disagreed with.
We probably knuckled down then because we were drawn against Kerry in an All-Ireland quarter-final which is a tough draw, so we had to mend the bridges and get on with it.
In 2013 Jim was away with Celtic, so the communication wasn't as much. I probably would have liked to get training a bit earlier in the year.
There was a difference with players coming in, I rated some of them differently to him. It just wasn't possible to mend it.
There was also a bit of controversy over the nature of his exit. Some claimed Gallagher walked away, while others have said that McGuinness was the one who made the decision.
The truth seems somewhere in between.
Gallagher claims he had made his mind up to leave the Donegal setup before a pivotal meeting, but his colleague attempted to push him out the door once he got wind of this. He also revealed that he hasn't spoken to McGuinness since.
We had a meeting with myself, Maxi [Curran], Pat [Shovelin], and Jim.
The previous day I had been at a sevens tournament and there was a few Donegal legends with me at it. I made it clear to them that the next morning I was jacking it in because it was going to be too fractured.
Jim tried to turn it on the table, so there's a disagreement over how it ended. That's the way it goes.
At the meeting we had a disagreement. It was a cold meeting, because things were frosty between me and him at that stage. There's no point saying any different.
There was way of repairing it. There was too much of a difference of opinion on players and the way forward with them. At the end of the day, we had a magical time. It was a brilliant period and I was happy to leave it at that...
I've never seen him since...
I think it is very unlikely (they will mend their relationship). You just move on in life and that's it.
If you feel you're wronged you get on with it.
An intriguing insight.
You can listen to the podcast in full here.