Jordan Owens struck a minute from time as Crusaders beat Ballinamallard 2-1 at Seaview to move within three points of league leaders Linfield.
The Mallards took a 44th minute lead when keeper Sean O'Neill spilled a shot and Mark Stafford pounced to score.
Eamon McAllister fired in the equaliser on 63 minutes before United's Jason McCartney was sent-off on 79 minutes for a rash challenge on Davy Magowan.
Owens netted from a rebound to clinch a crucial three points for the Crues.
Crues midfielder Chris Morrow saw his powerful shot tipped over by keeper Alvin Rouse in a pedestrian first half.
Stafford put the Mallards ahead just before the break by netting after O'Neill failed to hold Ryan Campbell's shot.
The introduction of McAllister and Gary McCutcheon in the second half sparked the Crues into life.
McAllister was perfectly placed to level after a Magowan header was cleared off the line.
McCartney was shown a straight red for his poor tackle on Magowan before Owens fired in the winner after Rouse fumbled a McAllister strike.
The last-gasp win completes an excellent four days for Stephen Baxter's team following the midweek victory over Linfield in the League Cup quarter-finals.