With all five of last season's games between Drogheda and Pat's in league and cup having ended in draws, this latest clash looked to be heading towards another stalemate until the game finally sparked into life in the final 20 minutes.
Drogheda's only real chance of the first half was a tale of three brothers when, after just five minutes, Ryan Brennan dispossessed older sibling Killian in midfield and sent Declan O'Brien down the wing to cross it for middle brother Gavin, who pulled the ball wide of Pat's far post.
After that, it was mostly one-way traffic in favour of Pat's with Anthony Flood and Chris Forrester looking lively up front. Drogheda midfielder David Cassidy and goalkeeper Gabriel Sava combined to clear a Kenny Browne header from under the crossbar after 34 minutes, while Flood headed agonisingly over from the resulting corner.
With a series of dodgy back-passes and scuffed clearances giving Pat's ample opportunity to score, the home side could count themselves lucky to be ending the first half on level terms.
Although Drogheda started the second half in a livelier fashion, Pat's looked in control until Gavin Brennan's low shot into the box bounced up and hit big brother Killian on the hand, earning the home side a penalty with just 20 minutes remaining. Unfortunately for the Drogheda supporters, O'Brien dragged his shot wide.
While Drogheda may have been relieved to see Flood taken off minutes after remonstrating with the referee about the penalty decision, his replacement, a bustling Christy Fagan, soon made an impact when he latched onto a low cross by Ger O'Brien to drill a low shot past Sava from the edge of the six-yard box for the opening goal with nine minutes remaining.
Drogheda looked to have snatched a draw from the jaws of defeat when Ryan Brennan smashed a volley into the roof of the Saints net on 90 minutes.
However, their celebrations proved to be short-lived as Alan Byrne, who had already been booked, suffered another ball-to-hand incident just inside the Drogheda box and Killian Brennan smashed the resulting penalty high to the goalkeeper's left to give Pat's the victory against his home-town club.
DROGHEDA – Sava; Quigley, Prendergast, R. Brennan, G. Brennan, Grimes, Rusk (Brady 77), Cassidy, O'Brien (Hynes 80'), Daly, Byrne.
ST PATRICK'S ATHLETIC – Clarke; O'Brien, Kenna, Browne (Price 45), Bermingham, Bolger, Russell, K. Brennan, Byrne (Kelly 64), Forrester, Flood (Fagan 75).
REF – T Connolly (Monaghan)