Managerless Kilmarnock suffered a fifth straight Ladbrokes Premiership defeat after Ilkay Durmus' first-half goal gave St Mirren a 1-0 win.
The Paisley side should have won far more convincingly but in the end one goal was enough to earn Jim Goodwin's men their fifth victory of the season.
Saints were without the ineligible Calum Waters, who could not play against his parent club. In came Tony Andreu, with Paul McGinn switching to left-back and Sam Foley to central defence.
Kilmarnock made two changes from the team beaten by Rangers. The suspended Alan Power dropped out alongside Mohamed El Makrini, replaced by Chris Burke and Eamonn Brophy.
The home side started brighter and had the first real chance. Cammy MacPherson's corner was met on the volley by Sean McLoughlin but his shot was blocked.
Killie, looking for their first goal in six matches, then passed up a great chance to get in front.
Niko Hamalainen picked out Liam Millar with a terrific cross but the frontman completely missed the ball in front of goal.
Brophy then worked Vaclav Hladky with a stinging drive that the goalkeeper did well to parry.
The home side then created a great chance. Durmus crossed from the left and Jon Obika was unfortunate to see his header drift over the crossbar.
Saints, though, went in front after 17 minutes. Andreu slipped a ball in to Durmus and the winger drilled a low shot beyond Laurentiu Branescu.
The former Hamilton forward then teed up Obika whose drive climbed over the crossbar and into the Killie fans behind the goal.
Next to threaten for Saints was Kyle Magennis, with the captain's 25-yard drive narrowly going over the top.
Osman Sow came on to replace the injured Rory McKenzie just before half-time. And he had Kilmarnock's first chance of the second period only for Hladky to deny the striker.
Saints were then awarded a free-kick after Gary Dicker tripped Durmus. MacPherson's strike was on target but Branescu saved well.
Junior Morias then set up another good chance for the home side with a mazy dribble. The ball broke on the edge of the box for Durmus but he couldn't get his shot on target.
Saints should have then sealed the game after 69 minutes. Obika played in MacPherson but the midfielder took too long to get his shot away and Kilmarnock recovered to block.
Morias then drove in a shot that the goalkeeper saved as the home side continued to waste chances.