But it is yet another hard luck story for the Buddies, who had already seen their opponents pinch the final place in the top six this season.

And they had further salt rubbed into their wounds as they saw a strong penalty appeal waved away before missing a string of golden chances – including substitute Collin Quaner's best impression of Chris Iwelumo at the Mount Florida end.

Connor McCarthy did pull one back late on but it was not enough to deny St Johnstone another date with destiny.

The 2014 winners saw their pre-match planning blown apart on Thursday when they announced two players had tested positive for coronavirus – with another couple ruled out through track-and-trace measures.

There was no sign of Stevie May, Liam Craig, Murray Davidson and second-choice goalkeeper Elliott Parish at Hampden, with on-loan Hearts stopper Bobby Zlamal drafted in on an emergency loan to fill a seat on the bench.

St Mirren were virtually at full strength, with striker Eamonn Brophy even making a surprise return among the substitutes having previously been told his campaign was over.

The first half was an open, gripping affair with chances at both ends.

And there was controversy too as St Mirren's claim for a penalty after 18 minutes was turned away.

Referee Willie Collum had his pick of infringements to choose from as Jamie McCart's caught Kristian Dennis on the boot when the Saints striker connected with Ilkay Durmus' cross, before the defender's outstretched arm then stopped the ball going any further. But the official decided neither was strong enough for a spot-kick.

Both sides had their keepers to thank for the game going in goalless at the break. First Alwnick pushed over Shaun Rooney's curling effort with a finger-tip stop.

St Johnstone's quarter-final hero Zander Clark then had to rescue his team again as he threw himself down to deny Lee Erwin.

It was a bad miss but Clark deserves the credit for making himself as big as possible.

And he produced another big save 10 minutes into the second half after Rooney's tumble let Durmus in.

Clark, though, had nothing to do with substitute Quaner's horror miss on 63 minutes.

Durmus tied Rooney in knots again before throwing over a sublime low cross but from the same spot where Scotland striker Iwelumo famously blew an open goal against Norway back in 2008, the German also somehow fired wide from point-blank range.

And predictably, that wasted chance was compounded as the Perth men grabbed the lead. Callum Booth led a counter attack as he found Middleton out wide, with his low ball across the face of goal was steered home by Kane.

Having set up the first, Middleton took all the credit for the second, winning a free-kick from Joe Shaughnessy before whipping the set-piece over the wall and past Jak Alnwick.

The Buddies keeper will have to explain why he was beaten so easily with the strike hardly in the top corner but he did at least respond with a fine save to deny Rooney's point-blank header.

Quaner fluffed another huge chance as he nodded wide at the front post but McCarthy did give Saints a lifeline as he headed home from Jamie McGrath's free-kick with four minutes left.

Jim Goodwin's team mounted a late siege but St Johnstone held on.