Donegal Celtic moved four points clear of the Premiership basement thanks to a Paul McVeigh strike against Glenavon.
DC striker Mark Miskimmin wasted an early chance before Lurgan Blues forward Guy Bates saw his free-kick saved by John Connolly.
Andy Coleman kept out Paul Bradley's header but DC made the breakthrough on 68 minutes when McVeigh flicked in from a Conor Downey cross.
Donnelly denied Gary Hamilton and Kris Lindsay as DC held on for the victory.
Donegal Celtic were under pressure to perform after manager Pat McAllister described Saturday's 5-0 defeat at Glenavon a "disgrace".
Both sides created openings in the first half while Glenavon enjoyed a spell of pressure after the break.
But the hosts netted the only goal through experienced McVeigh and the Lurgan Blues pressed for a late leveller.
Donnelly made two vital saved while Glenavon's Niall Henderson also went close for the visitors.