Former Republic of Ireland internationals Stephen McPhail and Keith Fahey were both sent off as Shamrock Rovers clung on for a 2-1 win at Tallaght Stadium that lifts them above the champions to third in the SSE Airtricity Premier Division table.
Hoops' midfielder McPhail was first to see a straight red on 59 minutes when he clashed with Killian Brennan, appearing to head butt the Saints' midfielder, after his heavy challenge on visiting right-back Conor McCormack.
Fahey followed 16 minutes later when he was dismissed for pushing over Rovers' left-back Rob Cornwall.
Unfortunately, they were the main talking points of a frenetic derby which was ultimately won by Gary McCabe's deflected second-half strike.
Both sides made two changes from their respective wins over UCD and Bray last week.
Rovers brought Shane Robinson and McPhail back into their midfield from the start while St Pat's saw Kenny Browne and Fahey return.
And it was Rovers, who have struggled to score goals at Tallaght all season, who had the perfect start with the lead inside two minutes.
McPhail fed in-form fullback Simon Madden on the overlap down the right and his low cross wasn't cut out as Dean Kelly scored for the second week running, side-footing past the hapless Brendan Clarke from close range.
St Pat's responded to level on 10 minutes in a high tempo opening.
It was almost a carbon copy of Rovers' goal as Fahey put Conan Byrne away on the right to whip over a low cross which resulted in Christy Fagan nipping in front of Jason McGuinness at the near post to stab home his 16th league goal of the campaign on his 100th Saints' appearance.
St Pat's dominated possession for much of the remainder of the first half, though without seriously worrying Rovers' ‘keeper Barry Murphy.
Rovers came alive again as half-time approached with Kelly having a header deflected over for a corner. McCabe then worked Clarke from a long-range free kick.
As in the first half, Rovers had the perfect start to the second as they regained the lead nine minutes in for what would prove the winner.
McCabe went on a run down the inside right channel and let fly with a speculative shot that appeared to take a deflection to flummox Clarke and loop over him into the far corner of his net.
But the red mist soon descended as first McPhail and then Fahey were sent off.
St Pat's pressed for the remainder of the game and almost snatched an equaliser right on 90 minutes when Mark Quigley and Byrne in turn saw headers come back off the Hoops' crossbar from Daryl Kavanagh's cross.
Robert Bayly should then have scored a third for Rovers three minutes into added time, but Clarke pulled off a terrific save.