Shamrock Rovers all but ended the title race with a dramatic late Nahum Melvin-Lambert own goal deciding an absorbing, if somewhat frantic, Dublin derby in Inchicore.
This was tough on the Saints, who had the chances to win the game, but runaway leaders Rovers have made a habit of late goals and they go nine points clear, with a game in hand; nobody is doubting that the champions will remain the champions going into 2022.
Officially there were no Rovers fans in the ground, but when the latest of Dylan Watts' ever-dangerous free-kicks was knocked into the back of the net by the Saints substitute, Hoops fans emerged from hiding to celebrate with the visiting bench, who jumped out onto the pitch to celebrate.
For Saints, this was another deeply frustrating late defeat to their rivals in Inchicore, but there was little in it throughout and even a draw would have made life next to impossible for the home side. They can look to build next season, but before all of that they are still in a battle to ensure European football next season.
This was not the prettiest of games, but it was hard to take your eyes away and Rovers have ended any concerns their fans might have about the destination of the trophy in a quietly ruthless manner.
Saints coach Stephen O'Donnell's faith in young defender James Abankwah was evinced with a powerful display from the centre-back.
There was a proper bite to the early exchanges. Recent addition Barry Cotter, who was named RTÉ's man of the match, was aggressive on the speedster Darragh Burns; Jamie Lennon snapped in on Richie Towell and the crowd was revelling in it all.
Rovers were caught offside thrice in the first 13 minutes, but Saints knew one slip could be crucial. The first chance of note, if it were even that, saw the powerful Lennon screw the ball wide from 25 yards.
A stunning Watts ball put Danny Mandroiu in, but his cross was cleared by Paddy Desmond. Pat's had a big penalty shout midway through the half when Darragh Burns appeared to be tugged down by Lee Grace, but nothing was given. Replays suggested referee Rob Hennessy got the decision right.
O'Donnell's side were happy to have all their players in their own half, but Rovers engineered a way through on 28 minutes. Cotter was put in by Gary O'Neill and his stretched pull-back found Mandroiu who blazed over the old Shed end.
Rovers were on top now and another little Watts pass put Mandroiu in, but he never fancied it from a tough angle. Pico Lopes headed into Vite Jaros' hands with two minutes left before the break in what proved to be the final chance of the half.
Saints had a smashing chance early in the second half. Bone's superb cross was met by the diving head of Chris Forrester, only for his header to go wide with Alan Mannus seemingly beaten.
Burns was putting himself in the shop window with his blistering start to the second half and he skinned O'Neill only or Forrester to fluff his shot after the Northern Ireland underage international's cross.
Burns again raided down the right 18 minutes after the break but after his cross substitute Billy King couldn't quite nurse the ball under control. Sam Bone's absolute rasper produced a superb save from Mannus on the hour mark.
The game was crying out for a goal that so nearly came. The best chance of the game came when Watts put substitute Aaron Greene through. Jaros opted to stay near his line rather than come out but Greene, befitting his career in some respects, failing to score when he really should have.
A frantic ending had the home fans nervous and a brilliant double save from Jaros to deny Towell and Watts kept their title hopes alive.
Or so it seemed, before an own goal condemned them to defeat.
St Patrick's Athletic: Jaros; Bone, Abankwah (Griffin 62), Barrett, Bermingham; Lewis, Lennon (McCormack 81), Forrester (King 56); Burns, Coughlan (Melvin-Lambert 81), Smith.
Shamrock Rovers: Mannus; Gannon, Lopes, Grace, Finn; O'Neill, Towell, Mandroiu (McCann 78), Watts, Cotter (Farrugia 75); Gaffney (Greene 65).
Referee: Rob Hennessy.