Shelbourne advanced to a potentially intriguing quarterfinal at home to Shamrock Rovers when a dramatic, 85thminute winner from skipper Pat Scully gave last year's double winners victory in a tense third round replay at Tolka Park.
The contest looked to be heading for extra time when up popped Scully to head home a Richie Baker free for a scarcely deserved victory.
Derry were adamant that the free should never have been awarded, arguing that central defender Joe Harkin did not foul Shelbourne striker Dessie Baker.
But now Shelbourne are very much in contention for an encore of last year's double success. But they will not have a more serious examination of their undoubted talent than that caused by a resolute Derry side.
Both teams started with the same line-ups as in the 1-1 draw in the first game at the Brandywell on Saturday, with Richie Foran again operating as a lone striker. With the strong wind in their favour in the opening 45 minutes, it was inevitable that Shelbourne enjoyed the bulk of the early attacking moves.
A Dessie Baker cross from the right set up an opportunity for James Keddy after just nine minutes. But the midfielder's volley from 14 yards was straight into the arms of goalkeeper Russell Payne.
But with Darren Kelly and Harkin in commanding form in the heart of the visitors' defence, Shelbourne were largely restricted to long-range efforts.
The visitors did look dangerous on their occasional breakaways, and from one Eddie McCallion corner on the right a 20-yard effort from Kelly flew just over the bar.
In the 48th minute, Shelbourne midfielder James Crawford took advantage of hesitancy in the Derry defence to supply a perfect ball for Foran. But with the goal at his mercy he shot wide.
Derry then went close when an Eamon Doherty cross was deflected into the path of Sean Hargan. But his shot at the far post was brilliantly blocked by the alert Steve Williams in the home goal.
In an effort to inject some life into his attack, Shelbourne manager Dermot Keely introduced Richie Baker as a substitute for Crawford on the hour with the home side reverting to a more orthodox 4-4-2 formation.
That move seemed to have the desired effect with Payne doing well to push out a snap shot from Dessie Baker after the Shelbourne man had skipped past two defenders. Foran then shot agonisingly wide after a neat interchange between Eoin Heary and Dessie Baker.
Eamon Doherty had a header shaved by the diving Williams as Derry again threatened on the counter-attack. The Brandywell team had a real let-off on 83 minutes when Richie Baker led the ball on for Foran. He swivelled and shot left-footed on the turn from the edge of the box only to see his effort rebound off the crossbar.
But Shelbourne eventually broke the deadlock and Derry's hearts just two minutes later when, after that controversial free, Scully's looping header beat Payne at the far post.
SHELBOURNE:Williams; Heary, Scully, McCarthy, Geoghegan; D Baker, Doolin, Fenlon, Keddy; Foran, Crawford. Subs: R Baker for Crawford (60 mins), Byrne for Doolin (88 mins), Hutchison for R Baker (89 mins).
DERRY CITY:Payne; McCallion, Kelly, Harkin, Hargan; Doherty, Hegarty, Hutton, McLaughlin; Devlin, Coyle.
Referee:H Byrne (Dublin).