St Mirren scored twice late on to extinguish Motherwell's spirited fightback and seal a League Cup final place for the first time since winning the competition in 2013.

Stephen Robinson's obdurate side were two up at half time after Mikael Mandron showed great reactions to fire in when Declan John's controversial corner, and Dan Nlundulu lashed in a wonderful second from 20 yards.

Substitute Callum Hendry provided hope for Motherwell late on, before Richard King's fortunate effort and Mandron's well-taken second sealed a final place.

The Paisley side will now face Celtic or Rangers at Hampden on 14 December, with the Glasgow pair playing in Sunday's second semi-final.

Former Motherwell striker Mandron smashed in his opener with perfect predatory instinct but there will be plenty of conjecture about the build up.

Motherwell were not only unhappy about what they felt was a soft free-kick award, but that the ball was still rolling when Alex Gogic fired it out to the left prior to John winning the set-piece.

Nevertheless, the Fir Park side moved on from their angst, spending even more time in St Mirren's defensive third as Apostelos Stamtelopoulos lasered a low shot from the edge of the box which made Shamal George work.

But just as Motherwell looked to be on top, St Mirren produced a sucker punch.

Fresh from his outrageous overhead kick against Hearts on Wednesday, former Southampton and Bolton forward Nlundulu showed he can score beauties from distance too, unleashing a right-footed shot which arrowed into the right corner.

Mandron nearly made the most of a Motherwell mix-up to score again, only to be denied by a post, and Killian Phillips might have had his sixth of the season if he'd been more accurate.

For a few minutes near the end, extra-time seemed a possibility as Hendry pulled a goal back for Motherwell by sweeping in Tom Sparrow's low centre.

But Jamaica international King replied almost immediately, his shot being blocked by goalkeeper Calum Ward before spinning outrageously up and into the net.

Then Phillips' brilliant strike off the crossbar fell to Mandron to curl home beautifully and seal St Mirren's win.

Robinson spent some of the build up to this semi-final insisting St Mirren aren't just a bustling, physical machine. The former Motherwell boss is adamant group are also very good footballers.

Mandron and Nlundulu showed that with their goalscoring prowess, while Jayden Richardson and John often operated classily on the wings as well.

But there's no doubt the stature through the St Mirren's spine is an absolute asset to the Paisley men, and there's nothing wrong with that. What the axis of Gogic, captain Mark O'Hara, Phillips and Mandron brings is invaluable.

People predicted Motherwell's movement and passing would be well-suited to the expansive Hampden pitch, and the likes of the rangy Emmanuel Longelo and Tawanda Maswanhise certainly enjoyed exploring it.

But Jens Berthel Askou's group lacked cutting edge. Elliot Watt's strike from distance was dealt with and Maswanhise dragged shots wide in both halves.

On another day, the Zimbabwean is more than capable of making teams pay.

St Mirren manager Stephen Robinson: "I am extremely proud of the players A lot of the comments before the game motivated the players today.

"We are a very good side and very well organsied - as everyone keeps reminding us - and we needed that in the second half, but we showed a lot of quality.

"There was some fantastic play and it could have been more. I thought they carried out the gameplan really well."

St Mirren goalscorer Mikael Mandron: "Sometimes you have games where everything just falls for you. Especially the second one, there was someone in front of me and it helps me just to bend it around him.

"I'm so happy. Since I left Motherwell, I don't think I've ever beaten by them, so today was perfect day to do that."

Motherwell head coach Jens Berthel Askou: "St Mirren executed the gameplan better than us, and they're deservedly in the final.

"We started okay after after a little bit of nerves, we applied some pressure, but our attacking game wasn't good enough and in the first, we were way too far off the level needed in the first-half.

"The game opened up in the second half when we were chasing, but they did well to punish us."

St Mirren host Hibernian in the Scottish Premiership next Saturday (17:45 GMT), but will have an eye on next month's final of this competition at Hampden.

Motherwell visit Aberdeen next Sunday (15:00).