Pierre Van Hooijdonk had snatched a first-half opener after the referee, Bill Crombie, ruled that the United defender Steven Pressley was guilty of a deliberate back-pass. Celtic, who had Brian O'Neil red-carded after 48 minutes, looked like having to settle for a point after a late Gary McSwegan strike, but in the dying seconds Mackay touched in from a yard out.
The home side made a solid start as the Celtic defence struggled to cope with the intelligent runs of McSwegan. In the 20th minute, Celtic threatened properly for the first time through the trickery of the Italian Paolo Di Canio, but his drive was blocked by Hannah. There was more danger for United moments later when Van Hooijdonk threaded a pass through to Andreas Thom, but the United keeper, Ally Maxwell, came off his line quickly to make the block.
The controversial opening goal came just before the interval. Referee Crombie ruled that defender Pressley had passed back to the goalkeeper after a dangerous through-ball by Thom. Despite United having ten players on the goal-line, Van Hooijdonk still managed to squeeze the short free- kick home.
The quality of Crombie's refereeing was also open to question three minutes after the break as he dismissed O'Neil. It seemed McSwegan had fouled him first but Crombie ruled against the Celtic defender and O'Neil was sent off.
From the free-kick, Hannah went close when his header was cleared off the line by Van Hooijdonk. United came close again in the 56th minute, when Dave Bowman fired in a shot from 25 yards which hit the crossbar.
With three minutes left, McSwegan equalised after he escaped from Hughes and lashed home his shot. But in the last seconds, Mackay touched home the winner after a header by Cadete came back off a post and rolled along the line.Reuse content