After two and a half years in charge, the axe finally fell on Jackie McNamara. After this minor disaster at McDiarmid Park, Stephen Thompson, the Dundee United chairman, had already decided before the 90 minutes were up that he was going to remove his manager immediately. It took Thompson little more than 10 minutes after the final whistle to relay the news.

The pity is, the United drama will contrive to obscure this St Johnstone win, which was all of exciting, heroic and calculating. Despite playing with 10 men for 67 minutes, Tommy Wright’s team stayed buoyant, constantly menaced their visitors, and were worthy winners. Wright once again showed what a thoughtful and proactive manager he is.

McNamara stood by the touchline, often motionless, while volleys of abuse were hurled at him by an angry United travelling support. Despite Alan Mannus, the St Johnstone goalkeeper, being red-carded after 23 minutes, McNamara’s team could not apply their advantage and were ultimately subjected to a humiliating defeat.

It was the last straw. After an abysmal run of form over the closing months of last season, United this season have one win in nine in the Ladbrokes Premiership and are mired in the early relegation talk. Having lost a spate of fine players over the past 18 months – everyone knows the truth of that – McNamara has paid for failing to create a new and worthy United team.

McNamara has been placed on immediate “gardening leave” – the new fad for sacking managers whereby the club seeks to protect itself legally and financially. Chairman Thompson now has to decide whom to place in charge for this Saturday’s match against Partick Thistle in Glasgow, and whether he can appoint a new manager in time for that. It would seem unlikely.

A host of names are already being thrown into the Tannadice ring: Tommy Wright, Ray McKinnon, Stuart McCall, Mixu Paatelainen, Jim McIntyre and more.

The writing was on the wall for McNamara when his team failed to pick apart the 10-man Saints. Mannus was red carded after 23 minutes for barging Billy McKay, who duly converted the penalty. But a Graham Cummins equaliser after 64 minutes and a Simon Lappin winner 10 minutes from time did for the visitors.

There were scores of chances at both ends, with Adam Taggart and Mario Bilate both missing good chances for McNamara’s men, but United’s football was edgy and lacking composure. The fault, as ever, was traced back to their manager’s door.

“I totally understand it [the fans’ frustration],” said United captain, Sean Dillon. “We’re not winning games, so of course I understand it. The fans aren’t the only ones that aren’t in good form. We need to try to stay positive.

“We lost two bad goals and we missed chances again. So we are disappointed. We got a break with their keeper being sent off, and we went a goal up. St Johnstone deserve credit for the way they came back at us, but we’ve still given them two goals.”

Dillon noted the anger of the United support, but insisted that, come what may, the players themselves have to remain strong.

“As a player you can’t get too up or down – you can’t afford to,” he said. “Fans can go from massive highs to major lows, but as a player you can’t do that. Yes, we feel devastated after a result like this, but you can’t be down for long. You’ve got to be ready to go again for the next game. If you hit rock bottom, what chance have you got?

“You’ve got to keep fighting. Everyone is in it together. Everyone wants to win games. We want to be challenging for trophies and be as high up the league as possible. But things are obviously magnified, and more questions are asked, when things aren’t going well.”

Away from United’s woes, Wright said later that it was one of the finest displays he had ever seen from a St Johnstone team in his near four years at the club. And it included losing Michael O’Halloran early in the game, who was already hobbling and was made the sacrificial lamb by Wright when forced to bring on Zander Clark, his substitute goalie, after Mannus’s dismissal.

What a week for St Johnstone – first dismantling Rangers at Ibrox and now this fine win.

“We had 10 men but we had that willingness to keep going, to go and win the game,” said Simon Lappin. “The way we didn’t want to settle for a draw was incredible. I thought everyone, just like last Tuesday night at Ibrox, was outstanding.

“You could sense in the game that we were on the up. We knew we would get chances. It wasn’t a case of settling for a point – we knew we could go and get the three points, and we did that.”