The FAI Cup holders unleashed their killer Ds on the league champions as they attempted to lay down an early season marker in Tallaght.
But while Eoin Doyle and Mark Doyle could have had St Pat’s home and hosed in the first-half, Shamrock Rovers hit back with a timely reminder of their strength in depth.
Skipper Ronan Finn cancelled out Eoin Doyle’s opener to force a penalty shootout after an entertaining game in front of 5,426.
Alan Mannus saved from Chris Forrester and that eventually paved the way for Jack Byrne to dink home the winning spot kick and curb the Saints enthusiasm.
Nobody should make sweeping assessments on the back of a glorified pre-season game, yet new look St Pat’s showed their appetite for a title fight this season.
Their large travelling contingent in the East Stand certainly enjoyed their first meaningful glimpse of this Tim Clancy era.
And while the Hoops only got going after the break, their fans appreciated the reassurance that experience in the ranks brings.
They started to tick when big guns like Graham Burke, Richie Towell and Rory Gaffney were introduced after the hour.
And with so much firepower at his disposal, Stephen Bradley will have some job keeping all of his leading lights happy.
St Pat’s tentative start gave way to a swashbuckling approach and Clancy’s forwards were soon relishing their battle with the champion’s rejigged defence.
Jack Byrne’s return to Rovers and Eoin Doyle’s return to the league - but with St Pat’s this time - were the biggest headline grabbing transfers of the close season.
But Doyle was a man on a mission here, causing all sorts of bother throughout that opening half.
Yet it was Mark Doyle, who played for Clancy at Drogheda last season, who could and should have had the Saints out of sight by the break.
Third highest scorer in the Premier Division last year, he pulled the trigger rather than square to Darragh Burns in space but his shot was easily mopped up by Alan Mannus.
But quite how he squandered his second opportunity is anyone’s guess.
When Sean Hoare failed to deal with a clearance, Eoin Doyle robbed him and surged into space.
He squared to his namesake but with only Mannus to beat, he took a swing and completely missed the ball in front of the South Stand.
Predictably enough, those Rovers fans slaughtered him but they also knew what a threat he and the other Doyle had been.
And those Saints chances kept on coming with Mannus saving twice from Eoin Doyle after a killer through ball from Chris Forrester.
Dylan Watts then had to clear a Jack Scott header off the line before Mannus kept out Mark Doyle’s follow-up in a crowded box.
League champions Rovers weren’t playing poorly as they enjoyed plenty of the ball, but they lacked the spark and have-a-go approach of the FAI Cup winners.
Aidomo Emakhu, one of the club’s rising stars, was lively but only in bursts and that flicker of hope was soon snuffed out.
Danny Mandriou - with the Hoops first effort on target - forced Josep Anang, the on loan West Ham goalkeeper, into a save just before the break.
But the Saints were just as tenacious in the second-half and got their rewards five minutes in when Eoin Doyle slotted home from close range.
Mark Doyle turned Sean Gannon inside out and found Jamie Lennon with the cross. But Mannus could only parry the midfielder’s shot into Doyle’s path.
Rovers upped their game with Richie Towell, Rory Gaffney and Graham Burke off the bench and deservedly pulled level in the 68th minute.
Anang made a complete mess of Farrugia’s cross at the near post and down low, he let the ball slip through his hands and skipper Finn stabbed home to force the shootout.
SHAMROCK ROVERS: Mannus 7; Gannon 6, Hoare 6, Grace 6; Finn 7 (Cotter 82, 5), O’Neill 6, Watts 6 (Gaffney 63, 6), Farrugia 7; Byrne 6, Mandroiu 6 (Towell 64, 6); Amakhu 6 (Burke 63, 7).
ST PAT’S: Anang 6; Scott 6, Redmond 7, Abankwah 7 (Grivosti 76, 5), Breslin 6; Lennon 7 (McClelland 86, 5), Forrester 7; Burns 6 (Owolabi 76, 5), King 6 (O’Reilly 60, 6), M Doyle 7; E Doyle 7.
Referee: R Harvey 6
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