Cavan Gaels defeated St Eunan's 0-8 to 0-7 in Sunday's AIB Ulster Club Football preliminary round clash.
Rory Kavanagh tries to get away from Eamonn Reilly
Dominant St Eunan's led 0-4 to 0-0 after 15 minutes and also had a goal controversially disallowed with John Haran adjudged to have overcarried.
However, Anthony Forde opened Gaels' account on 19 minutes and the sides were level at 0-4 apiece at the break.
Gaels then edged 0-6 to 0-4 ahead and while Eunan's levelled, Martin Dunne and Micheal Lyng frees proved enough.
St Eunan's started without Brendan Devenney who has opted to take a break from football for the remainder of the year after being troubled by injury this season.
However, the Letterkenny outfit didn't appear to be missing Devenney early on as his replacement Ross Wherity, Paddy McGowan, Mark McGowan and David McGinley knocked over points.
However, St Eunan's were angered when Haran had the ball in the net after a great run and finish only to have the score ruled out for overcarrying.
The disallowed goal proved to be the turning point in the match as Cavan Gaels finally found some form.
Anthony Forde opened Gaels' account in the 19th minute and further scores by Micheal Lyng and Seanie Johnston (two) had the sides level by the interval.
Members of our county board were collaborating with them and it was disappointing
St Eunan's manager Brendan Kilcoyne
Another Johnston score helped extend the Cavan outfit's lead to 0-6 to 0-4 early in the second half but Eunan's hit the next two points to level again with Wherity on target for the Donegal side.
With defences on top, scores were hard to come by during the final 20 minutes of the match and Micheal Lyng's two points were to prove decisive, despite Paddy McGowan's final score of the match for Eunan's.
Earlier in the second half, McGowan had missed a glorious goal chance for Eunan's.
After the match, angry St Eunan's manager Brendan Kilcoyne claimed that members of the Donegal county board had "collaborated" with Cavan Gaels prior to the game.
Kilcoyne alleged that an unnamed member of the county board had sent videos of recent St Eunan's games to the Cavan Gaels club.
"Members of our county board were collaborating with them and it was disappointing," said Kilcoyne.
Kilcoyne also insisted that Haran's first-half effort should not have been disallowed.
"We felt it looked like a good goal. We were three points up at the time and I felt it was a decision based on the scoreboard."