Ten-man Bohemians qualified for Europe for the first time in seven years by battling to scoreless draw at St Patrick's Athletic.
For the Saints, they can still join their Dublin rivals in the Europa League but must beat fellow challengers Derry City on Tuesday to stand any chance.
Bohs, fresh from beating champions Dundalk last week, were busy from the off but James Talbot was the first goalkeeper called into action on four minutes. He stuck out a vital hand as Saints striker Gary Shaw tried to round him after breaking into the box.
At the other end, a free-kick conceded near the end-line on the right by Ian Bermingham offered Bohs their first opening on 20 minutes. Keith Ward's low centre deceived the home defence but the unmarked Aaron Barry wasted the rehearsed move by miskicking his first-time effort.
Seconds later, Pat's fashioned their best chance, also from a free-kick. James Finnerty's grappling of Shaw incurred a booking which would later cost him but Chris Forrester almost immediately made him pay with the 20-yarder over the wall which Talbot brilliantly leapt got across his line to bat away.
Ciaran Kelly saw a couple of volleys from corners clear the Bohs crossbar, as did Ronan Hale from Darragh Markey's inswinging free-kick.
But the closest Saints came to breaking the deadlock was again through Forrester.
The former Bohs playmaker has endured a quiet season by his standards but showed his class two minutes before the interval by forcing Talbot to go full-stretch and tip his rising shot out for a corner.
The Saints' players, most of them playing for contract extensions, maintained the pressure after the break.
Kelly should have done better with a shot after striding forward but Hale's claims for a penalty following a tussle with Keith Ward were desperate.
The Ireland Under-21 striker did manage to get a sight at goal on the hour, only to waste it by lifting the ball over from 12 yards.
A minute later and Stephen O'Donnell's side earned a numerical advantage. The Bohs defence had been testing Neil Doyle all evening and a clumsy challenge by Finnerty on Shaw led to his second booking.
The rookie boss decided to go for it, introducing strikers Glen McAuley and Mikey Drennan, coupled with a switch to three at the back.
Aside from another Forrester effort which whistled past the far post, however, Pat's showed little to end their barren run in front of goal.
Another substitute Rhys McCabe forced Derek Pender to clear off the line as they scrambled for a winner late on but dogged Bohs held on for the precious point they required.