Curtis Main grabbed the only goal in Paisley to send St Mirren into the cinch Premiership top six and leave former club Motherwell locked on 20 points with three other teams at the bottom.
Main struck from close range in the 16th minute to earn Stephen Robinson’s side only their second win in 10 league games, although it stretched their unbeaten home run to 12 matches since losing to Motherwell on the opening day of the season.
Motherwell dominated possession but often lacked a cutting edge as their run without a league win extended to nine games.
The Lanarkshire side confirmed the signing of Riku Danzaki before the game but the Japanese attacker was not in the squad, and nor was striker Mikael Mandron, who netted two goals on his first start in the previous weekend’s Scottish Cup win against Arbroath.
Well boss Steven Hammell lined up with Kevin van Veen and Connor Shields up front with Stuart McKinstry playing at the head of a midfield diamond, and he will hope his recent signings can deliver quickly after Ross County’s win closed the gap at the bottom.
Scot Tanser came close for the hosts but Motherwell had more of the ball in the opening stages without testing Trevor Carson. Blair Spittal and McKinstry had shots blocked following good moves.
Saints took the lead in the 16th minute after Alex Greive’s flick sent Ryan Strain heading towards the bye-line. The Australian delivered a low cross and Main got in front of Shane Blaney to divert the ball past Liam Kelly from close range.
Motherwell had a penalty claim four minutes later when Ricki Lamie claimed he had been hauled to the ground by Charles Dunne, but referee John Beaton was not called to the monitor. A nudge from Lamie before the alleged foul may have put doubt in video assistant Grant Irvine’s mind.
Strain hit a free-kick straight at Kelly and there was little other action for the remainder of the first half.
Motherwell came close just after the interval when Lamie headed Spittal’s corner just wide of the far post.
The visitors’ first shot on target came in the 72nd minute when substitute Olly Crankshaw set up right-back Max Johnston, whose powerful left-foot drive was held at the second attempt by Carson.
Saints substitute Jonah Ayunga had threatened after turning Blaney but he was soon going back off after picking up an injury.
Main fired wide from a half chance before St Mirren survived a stoppage-time scare when Alex Gogic cleared off the line from McKinstry after Crankshaw’s cross had caused panic.