Caolan Boyd-Munce hit a spectacular first goal for St Mirren to send the Buddies past Motherwell and into the League Cup quarter-finals.
The former Northern Ireland Under-21 international replaced injured captain Mark O’Hara ahead of the previous weekend’s win over Dundee, which sent St Mirren top of the cinch Premiership overnight.
And the 23-year-old again helped alleviate the absence of O’Hara as he proved the difference in a 1-0 victory in Paisley.
Boyd-Munce lit up a scrappy start to the game in the ninth minute. Ryan Strain made some progress as he cut in from the right before the ball broke for the former Middlesbrough and Birmingham midfielder, who fired a first-time effort into the top corner from 20 yards.
Motherwell improved after a poor first half but did not do enough to prevent only their third defeat in six months under manager Stuart Kettlewell.
The visitors, with Davor Zdravkovski making his first start in midfield, were sloppy in possession for spells in the first half and struggled to get men forward to support their strikers as they played into a strong wind.
Keanu Baccus twice threatened for St Mirren after Motherwell lost possession well inside their own half.
The visitors’ first real threat came early in the second half when Theo Bair took in Stephen O’Donnell’s pass with his back to goal and fired a shot which Zach Hemming tipped over at full stretch.
Kettlewell brought on Lennon Miller and Mika Biereth before the midway point in the second half as the game became more open.
Good work from former Motherwell striker Mikael Mandron sent Conor McMenamin clean through but he delayed his shot and Dan Casey got back to block the effort.
Motherwell somehow got a three-on-two break moments later, but Callum Slattery’s pass did not allow Biereth the best angle to shoot and the Dane’s driven ball across the face of goal just evaded Conor Wilkinson.
Kettlewell switched tactics in the 76th minute as forwards Joe Efford and Mark Ferrie replaced wing-back O’Donnell and Wilkinson.
Former Well manager Stephen Robinson responded by putting on ex-Fir Park defender Charles Dunne and St Mirren saw out the final stages without serious threat.
Motherwell defender Shane Blaney had an opportunity to show his prowess from a 25-yard free-kick but the Irishman fired well over and Olutoyosi Olusanya had two great chances to make it 2-0 in stoppage time. The substitute was denied by Liam Kelly and then hit the post on the breakaway.