An injury-time Chris Kane goal saw St Mirren lose in Perth. Stephen Robinson's men created a host of chances throughout the 90 minutes, but couldn't find the net before Kane - who saw his penalty saved but scored on the follow-up - consigned Saints to defeat.
Lewis Jamieson made his first start of the season in place of Conor McMenamin, while Charles Dunne replaced the injured Richard Taylor in the only changes from the side that lost 2-0 to Rangers at Ibrox on Sunday.
The hosts were forced into an early change with Max Kucheriavyi having to be replaced by Sven Sprangler with just 10 minutes of the clock after failing to shake off the effects of a clash of heads with Scott Tanser in the opening minutes.
Saints should have taken the lead on 24 minutes when St Johnstone's Daniel Phillips gave the ball away on the edge of his box. The ball was worked through to Jonah Ayunga who was challenged just before he could slot into the net. It did fall to Jamieson whose effort was knocked over the bar by Dimitar Mitov in the St Johnstone goal.
The home side then had their best chance of the match on the half-hour mark when Matt Smith met a dangerous ball swung in by Graham Carey. The St Johnstone midfielder got his foot on it but sent his side-foot volley straight into the arms of Zach Hemming. Carey had a go from distance a few minutes later but didn't get enough on it to trouble the Saints goalkeeper with Hemming collecting with ease.
Saints were forced into a first-half change of their own when Ryan Flynn pulled up with an injury and was replaced by McMenamin. Stephen Robinson was forced into another change at the break when Tanser had to come off. He was replaced by James Bolton.
The Buddies should have taken an early second-half lead when Mark O'Hara found Greg Kiltie unmarked in the St Johnstone box. The forward headed into the ground which allowed Mitov to gather comfortably. The hosts then went up the park moments later with Hemming doing well to touch Carey's cross-cum-shot away from the danger area.
Jamieson did well to pick out a super cross-field ball from McMenamin on the hour mark. The St Mirren Youth Academy graduate brought the ball under control before getting his strike away, but it was straight at Mitov.
That would be Jamieson's last contribution as he was replaced as part of a double change on 66 minutes. He was replaced by Toyosi Olusanya while Mikael Mandron came on in place of Ayunga.
The substitutes can agonisingly close to putting us ahead on 72 minutes when Olusanya stole the ball in the St Johnstone half and race forward towards the box. He slid the ball across the face of the area where Mandron was sliding in, but his touch came off the post. That chance had come two minutes after Dunne had almost given us a stunning lead with his effort from 25 yards touched over the bar by Mitov.
The home side had the best chance on 78 minutes when substitute Kane pounced on a defensive mistake from Alex Gogic to race clear on goal. But the St Johnstone forward couldn't make it count as he dragged his attempt wide.
It appeared that it would be a share of the spoils for both sides until the hosts were awarded a penalty in the final seconds of the game. Kane saw his spot-kick saved by Hemming, but he followed up to win it for the home side.
Full-Time: St Johnstone 1-0 St Mirren
St Mirren: Hemming, Fraser, Gogic, Dunne, Flynn (McMenamin 45), O'Hara (c), Boyd-Munce, Tanser (Bolton 46), Jamieson (Olusanya 66), Kiltie (Baccus 76), Ayunga (Mandron 66)
Subs Not Used: Urminsky, Small, Nahmani, Greive
St Johnstone: Mitov, Gordon, McGowan, Robinson, Brown, Phillips, Smith, Gallacher, Kucheriavyi (Sprangler 10), Carey, Jaiyesimi (Kane 62)
Subs Not Used: Richards, Costelloe, Olufunwa, Jephcott, May, Turner-Cooke
Referee: Kevin Clancy
Assistant Referee: Drew Kirkland
Assistant Referee: Stuart Stevenson
Fourth Official: Ross Hardie
VAR: Alan Muir
Attendance: 2449
Match report image: PPA
