Shamrock Rovers’ late switches had the desired effect as a spectacular last minute winner in front of the away turned Tolka Park into a sea of Greene.
Striker Aaron Greene netted within six minutes of his introduction as Rovers withstood a sturdy Shelbourne comeback to move back within three points of leaders Derry City.
He sent an unstoppable shot into the top corner of the Shelbourne net after linking up with fellow subs Neil Farrugia and Danny Mandroiu in front of the away fans.
For long periods of the second half, it looked as if the home side - with manager Damien Duff facing his former club - was the more likely to land a winner.
They had threatened little before Shane Farrell slotted home at the back post on the hour to cancel out Andy Lyons’ second-minute opener.
From there, either side could have won it as both managers made attacking changes, but it was Greene who made the telling contribution at the death.
Such an exciting finish would have been difficult to predict during a first half that Rovers controlled without adding to Lyons tidy finish.
The wing back slotted home his third goal in two games with virtually the first move of the game as he beat Shels keeper Brendan Clarke.
Richie Towell profited from good work by Rory Gaffney and Ronan Finn before feeding the underlapping, who dropped a shoulder before picking out the bottom corner.
Dan Carr, who had a stint with Rovers four years ago, had Shels’ first effort on goal but he could only sidefoot straight to Alan Mannus.
Graham Burke shot marginally wide as Rovers enjoyed long spells of possession without producing much of note in front of goal.
That changed two minutes from the break when a slick passing move released Lyons in the box but this time he couldn’t find the target.
That miss became more costly as Shels levelled against the run of play, sub Shane Griffin coming up with the goods a minute after his introduction with a pinpoint cross for Farrell.
Gaffney was wasteful as he scuffed a good chance in the box and Burke again failed to hit the target, but it was Shels who produced the next big chance.
Dan Hawkins swung a free kick from the right deep towards the back post and ex-Rovers defender Luke Byrne saw his header just clear the top corner.
Greene made that pay a minute from the end of normal time as he rifled home, prompting a sea of green flares to light up the Ballybough End.
Shelbourne: Brendan Clarke; Aaron O’Driscoll, Luke Byrne, Kameron Ledwidge; John Ross Wilson, Mark Coyle, Aodh Dervin, Jordan McEneff (Daniel Hawkins 59), Conor Kane (Shane Griffin 59); Shane Farrell (Stanley Abnaebonam 86), Dan Carr (Sean Boyd 78).
Shamrock Rovers: Alan Mannus; Sean Gannon, Sean Hoare, Lee Grace; Ronan Finn (Neil Farrugia 83), Jack Byrne (Dylan Watts 72), Gary O’Neill, Andy Lyons; Richie Towell (Aaron Greene 83), Graham Burke (Danny Mandroiu 77), Rory Gaffney.
Referee: Damien McGraith
