Shamrock Rovers' title celebrations continue to be put on hold as Derry City deservedly saw the ten men off 2-1, at the Ryan McBride Brandywell Stadium.
Goals from Brandon Fleming and Sadou Diallo put City into a 2-0 lead and despite Rory Gaffney's stoppage-time consolation goal, it wasn't enough for the Hoops, who had defender Lee Grace also dismissed just after the hour mark.
Rovers had the first opening on seven minutes but Graham Burke's long range shot from the left-hand angle of the box was tipped away by a diving Brian Maher.
The Dubliners gaffer Stephen Bradley and his assistant Glen Cronin arrived at the ground, after finishing the Dublin Marathon in the morning and getting a quick helicopter ride to Foyleside.
City took the lead on 25 minutes as Fleming raced down the left before getting half a yard away from Darragh Nugent and seeing his whipped in cross-cum-shot sail over Ed McGinty and into the net.
The Brandywell men suffered an injury set-back four minutes later when Mark Connolly, who seemed to injure his knee had to be replaced by Sam Todd.
Rovers, who dominated possession throughout the first half, had half chances with Grace and Burke both having efforts gathered by Maher. Tiernan Lynch made another change at half-time with Diallo coming in for Robbie Benson, as the Foylesiders tried to get a better grip of things in the middle of the park.
On 50 minutes a superb run out of defence by Roberto Lopes ended with his pass finding Michael Noonan, who in turn saw his low centre find Josh Honahan at the back post, but the left wing back's close range shot was blocked by Ronan Boyce.
Minutes later Michael Duffy's left-wing free-kick was rolled to Diallo on the edge of the box, but his shot was straight at McGinty.
McGinty had to make another big save on 61 minutes, this time at full stretch, he did well to keep out Duffy's dipping 25 yard free-kick.
The visitors were rightfully reduced to ten men when Grace was cautioned twice in a matter of minutes when he fouled Fleming on both occasions, leaving referee Paul McLaughlin with no option but to dismiss the defender.
Bradley decided City were on top and he needed to tighten up at the back with Dan Cleary replacing Aaron McEneff, and Rory Gaffney came on for Noonan, to bring more experience to the forward line.
Derry sealed the win on 87 minutes. Duffy robbed Lopes down the right hand touchline before calmly squaring the ball to Diallo, who fired high into the net giving McGinty no chance.
Right at the death Gaffney turned the ball home from close range after Conor Malley's centre had picked out the big front man inside the six yard box.
Derry City: Brian Maher, Ronan Boyce, Cameron Dummigan, Mark Connolly (Sam Todd 29'), Jamie Stott, Brandon Fleming; Carl Winchester, Robbie Benson (Sadou Diallo HT); Gavin Whyte (Adam Frizzell 69'), Adam O'Reilly; Michael Duffy.
Shamrock Rovers: Ed McGinty, Darragh Nugent (John McGovern 79'), Lee Grace, Roberto Lopes, Cory O'Sullivan, Josh Honohan; Dylan Watts (Conor Malley 79'), Matt Healy, Aaron McEneff (Rory Gaffney 66'); Graham Burke; Michael Noonan (Dan Cleary 66').
Referee: Paul McLaughlin (Monaghan).
