Donegal's Marty McGrath tries to block Michael Greaney's strike
Monaghan hurlers defeated Donegal 1-15 to 1-14 in Sunday's Ulster Senior Hurling Championship clash at Clones.
A late point from sub Pat O'Connor proved decisive as Monaghan edged ahead again after Donegal's brave fightback.
Michael Greaney's early goal helped Monaghan lead 1-9 to 0-6 at half-time while Enna MacSuibhne also fired over some great points.
However, Kevin Campbell's 60th-minute goal sparked Donegal's revival before O'Connor's late point sealed victory.
Greaney fired in Monaghan's goal on five minutes while Stephen Lambe joined MacSuibhne in impressing for the home attack in the opening period.
Brian Phelan excelled in the Farney County midfield in the first half while Donegal needed Marty McGrath to produce a brave block to prevent Greaney notching a second Monaghan goal before the interval.
However, Kevin Campbell, Niall Campbell and Barry Friel did get on the scoresheet for Donegal as Monaghan led 1-9 to 0-6 at the interval.
Monaghan still led by six when Kevin Campbell drilled in Donegal's goal from a 20-metre free with 10 minutes left.
The two Campbells hit two more Donegal points and Sean McVeigh's score levelled matters with a minute of normal time remaining.
Extra-time looked on the cards but O'Connor's injury-time strike earned Monaghan a berth in the semi-finals.