Kearney said: "You get that gut feeling when it goes to extra time.

"It has been well-documented that Vaclav has had a tough time in the last couple of months and sometimes you just feel things are written in the stars and I was very confident when it went to penalties.

"I just thought he had the big saves in him.

"I am delighted for him on a personal level and that type of performance probably puts him down in history."

After the sides had fought out a goalless draw at Tannadice on Thursday night,  United attacker Nicky Clark  scored from the spot in the 23rd minute, before Saints forward Danny Mullen levelled three minutes later.

There were no more goals after the break, nor in extra time, with Saints substitute Duckens Nazon given a straight red card by referee John Beaton after 114 minutes for his aerial challenge on United defender Mark Connolly.

In the tension-filled shoot-out, Hladky made saves from Peter Pawlett, Pavol Safranko and Callum Booth, with Osman Sow hitting the post.

Paul McGinn and Mihai Popescu scored  for the home side, which ultimately rendered Mateo Muzek's strike  against the post as irrelevant.

Kearney, who took over from Alan Stubbs after just four league games, brought in a whole new team of players in January and he believes it could be 10 years before his squad realise the magnitude of their achievement.

"I said in the dressing room after the game that firstly, it was credit to the players who have been here all season and also credit to the players who came in in January," he said. "Between us we managed to gather some momentum at the right time of the season and carry that through.

"I don't think they will realise what an achievement this is for months, years. It might be five, 10 years down the line when they really understand the turnaround we had this season and what it led to today. I am delighted for everybody at the club."

United boss Robbie Neilson revealed his side did practise penalties beforehand.

He said: "It is the cruellest way to lose a game of football.

"It was very evenly matched over two games and extra time and it came down to penalties and ultimately someone has got to lose it. Unfortunately today it was us.

"We missed the first one, it gives them a lift and they score it and put the pressure on.

"We practised a number of times for the final, the semi-final, but there is different pressure.

"But credit to St Mirren, they scored their penalties, most of them.

"It is part of football, somebody has to lose. Unfortunately it was us."

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