Shamrock Rovers - 1 Waterford Utd - 2: Daryl Murphy scored twice, the second a stunning last-minute goal worthy of winning any match, as Waterford came from behind to upstage a Rovers side who failed to turn their dominant possession into goals.
Under-21 international Murphy, thoughtful and subtle throughout, had already got some reward when equalising Terry Palmer's opener for Rovers on 72 minutes.
The Blues' captain then collected substitute Steven Grant's flick from a Kevin Waters cross to power a dipping volley from 20 yards past Noel Mooney at his near post to snatch the three points at the death.
That completed an unlikely comeback by Waterford after Rovers had finally brought the game to life with the lead goal on 67 minutes. Shane Robinson nodded Keith Doyle's deep corner back across goal and Palmer headed home.
Waterford hit back five minutes later when Kevin Waters and Mark Clifford worked the opening to find Murphy who somehow squeezed the ball home from an acute angle under pressure from both Steven Gough and goalkeeper Mooney.
Rattled by Murphy's quick equaliser, Rovers were then reduced to 10 men on 75 minutes when Stephen Grant was shown a straight red card by referee Ian Stokes for a reckless challenge on Dave Mulcahy.
Grant had been guilty of two misses in a turgid first half. On both occasions the Rovers' spearhead was played through by a sublime ball from Keith O'Halloran. The first, on 34 minutes, he crashed off the foot of David Hennessy's left-hand post.
If that was a little unfortunate, Grant's second effort a minute before the interval was deplorable.
The benefit of having more time perhaps proved a hindrance as Grant skied his right-foot shot at least 10 yards wide with only Hennessy to beat.
The Waterford goalkeeper had earlier made the best save of the half from Trevor Molloy after the Rovers' winger had skilfully turned past Alan Carey to shoot.
Waterford were well in the game, however, with the languid touch of Murphy a real threat to Mooney's goal. The striker crossed to set up Kevin O'Brien to head, and then shoot, straight at Mooney in quick succession.
SHAMROCK ROVERS: N Mooney; Croly, Gough, Palmer, Doyle; McArdle (Rutherford, 77 mins), O'Halloran (Deans, 85 mins), O'Brien; Robinson, Grant, Molloy.
WATERFORD UNITED: Hennessy; Coleman (Grant, 63 mins), Breen, Purcell, Carey; Bruton (Waters, 63 mins), O'Brien, Mulcahy, Clifford, Quitongo; Murphy.
Referee: I Stokes (Dublin).