Steve Lomas' side had, much to his chagrin, not played a match since beating Kilmarnock at McDiarmid Park on March 9 but their patience was rewarded when Liam Craig bulleted a header past Radoslaw Cierzniak to earn the crucial point.
At the same time, the goal confirms Ross County's place and leaves Dundee United's own ambitions of finishing in the upper half of the division out of their own hands. Having led since midway through the first half thanks to a first senior goal by Ryan Gauld, Jackie McNamara's side weathered increasing Perth pressure, and the dismissal of Stuart Armstrong for diving with 11 minutes remaining, before finally succumbing.
In truth, the point was the least St Johnstone deserved for a performance that grew as a young United side wilted. Cierzniak made several saves at the visitors came under increasing pressure but was finally beaten when Craig scudded Mehdi Abeid's tempting corner into the net.
"It was just that little bit of quality we needed," said Lomas. "It was a bit harum scarum and they harum scarumed better than us in the first half and we looked like a team who had had three weeks off, but we showed more composure after the break."
Until then, the composure was reserved for the youngest player on the park. Gauld, making his first start after four eye-catching cameos, was United's most influential attacking force.
The diminutive playmaker might have required his parents' permission to be out this late on a school night but he did not look out of place among the adults.
Brave in possession, ambitious in scope and perceptive in his movement, the 17-year-old roamed menacingly infield from his right-sided role with an elusiveness that discomfited Tam Scobbie, in particular. Indeed, it was from one such sortie that he scored. Mark Millar caught Craig in possession inside his own half and managed to prod the ball into the space between St Johnstone's centre-backs and into the path of Gauld, who was scampering forward like a dog after a stick. As goalkeeper Alan Mannus rushed out to meet him and Steven Anderson lumbered across, it momentarily appeared as if the youngster would be overcome by fear but instead he jabbed out a foot to send the loose ball skidding into the unattended net.
The goal was a sloppy one for St Johnstone to concede, particularly given United were struggling to cleave openings on their own accord, but it was indicative of a listless first-half performance by the hosts. The Perth side found it hard to gather periods of prolonged possession but found their territorial superiority allowed them more sights of goal than their visitors. That each came from set pieces spoke of their disjointedness, though. Murray Davidson headed a Craig corner over under pressure from Keith Watson, Dave Mackay speared a free-kick over the crossbar and Steven MacLean finally forced a save from Cierzniak after meeting a Rowan Vine corner with a cute near-post flick.
Perhaps St Johnstone's struggles should have come as little surprise. They might not have been beaten at McDiarmid Park since late November but it is 13 years and 17 matches since they last overcame their Tayside rivals in a league game. To add a little context, Gauld was yet to start school. That record remains, but it mattered little after Craig's equaliser.
How St Johnstone had not hauled themselves level before then remains a mystery, particularly after an astonishing few seconds just after the hour. First a Craig scud was acrobatically pushed past by Cierzniak then, from the consequent corner, Davidson's towering header was cleared off the line by Barry Douglas but only as far as MacLean, whose effort was tipped on to an upright by the goalkeeper before bouncing across the face of goal and being slashed clear by Keith Watson.
United, by this stage, were finding it difficult to get out of their own half and, when they did, could make little impression on the St Johnstone goal. Michael Gardyne floated an arcing effort harmlessly over but the visitors' rhythm was further disturbed by the dismissal of Armstrong. The Scotland under-21 captain had been booked in the early exchanges and, having perpetrated another two or three fouls, might have been withdrawn by McNamara, but the decision was taken out of the manager's hands when Iain Brines deemed the midfielder to have dived under duress in the St Johnstone area.
"I'm not sure as I haven't spoken to Stuart yet," said McNamara of a decision that television pictures suggested was correct.
After that, United were camped in their own area, with 16-year-old John Souttar at the centre of the resistance after an injury to Brian McLean. A misjudgment by the youngster should have been punished by MacLean, while Davidson spurned two good openings before Abeid claimed a penalty for handball. Finally, however, the patience of the Saints was rewarded by the intervention of Craig.