When the full-time whistle sounded on a pulsating, madcap Europa League occasion, Mauricio Pochettino turned on his heel, avoided contact with anybody – friend or foe – and marched briskly off down the tunnel. In metaphorical terms at least, the steam was blasting from the Tottenham Hotspur manager’s ears.

This had been billed as the occasion when Spurs would erase the shoddiness of their first-leg defeat in Ghent and make a statement in European competition. Instead, it became one filled with recrimination and no little embarrassment because make no mistake, a club with Tottenham’s ambitions must be capable of disposing of opposition as modest as this.

Gent had arrived at Wembley in eighth place in the Belgian league and on a run of three wins in 12 matches in all competitions – one of them against Tottenham. It would turn into an unforgettable night for their management and players, together with the 7,000 travelling fans who packed one part of the stadium.

Tottenham camped inside the Gent half for virtually the 90 minutes, peppering shots at their goal but the visitors were able to break out and land the knock-out blow with eight minutes to go – the substitute, Jérémy Perbet, sweeping home after Kalifa Coulibaly’s pass had ricocheted off Eric Dier.

Pochettino’s team had lurched from the comfort of the lead that Christian Eriksen had given them on the night to the sense of panic after Harry Kane’s own goal, which had looped in off the top of his head as he tried to defend a corner.

Play Video 1:53 Pochettino: Europa League exit is 'no time to cry' for Spurs – video

But the deepest stain on the evening from their point of view was the straight red card that Dele Alli received in the 39th minute for his lunge at Brecht Dejaegere, which was a potential leg-breaker. It left Tottenham needing to score two goals, at least, with 10 men and a part of the frustration for Pochettino was that they looked like pulling it off.

Victor Wanyama advertised the comeback with a stinging finish but they paid for their overall lack of ruthlessness with the final pass or shot and they would be picked off by Perbet.

Pochettino went through the range of emotions in his technical area and the adrenaline threatened to overload his system as he repeatedly threw his arms up in the second-half in a call for more noise. How the crowd responded. There was times when Wembley was rocking, which bodes well ahead of Tottenham’s residency at the stadium next season.

But in the aftermath of defeat, it was inevitable that the focus would turn to the self-inflicted wounds – and none of them were clearer than the Alli sending-off. The 20-year-old, who has lost something of his spark in recent matches, was upset that Dejaegere had not been pulled up for a foul on him moments earlier and he was then angry at himself for losing the ball to his opponent with a heavy touch.

He took it all out on Dejaegere, jumping into a reckless tackle that saw him fly over the ball and slam the studs of his right boot into the upper part of the Belgian’s shin. Dejaegere’s leg buckled horribly and there was reason to be thankful that he was not seriously injured, although he would be forced off eventually.

Pochettino refused to castigate Alli. “Dele is very disappointed and sad – he knows he made a mistake but this is football and it can happen,” he said. “It’s now time to give him support.”

His opposite number, Hein Vanhaezebrouck, was also charitable towards Alli, saying that there had been no malicious intent to the challenge, however dangerous it was, and he was magnanimous in a more general sense.

His first act of the post-match press conference was to apologise for having stolen the result. “I like to win games that we deserve to win,” Vanhaezebrouck said. “Tonight we were not good but we made the difference in the first-leg, when we showed that we could play football.”

Vanhaezebrouck said that he had been nervous from the first whistle, having got the impression “some of the guys were not themselves”. He added that it “could have been over after 20 minutes”, had Tottenham added to Eriksen’s cool finish after a defensive lapse from the visitors but those words only seemed to make Tottenham’s subsequent failure all the harder to take.

Pochettino’s full-strength team, which had featured a three-man defence at the outset, were in charge but the complexion of the tie changed sharply when Stefan Mitrovic headed back a deep corner – which had been erroneously awarded – and Kane jumped in front of Moses Simon to inadvertently flick the ball past Hugo Lloris.

Tottenham played with bravery in the second-half and they were rewarded when Wanyama thumped a right-foot shot across Kalinic and into the far corner, after good work from Kyle Walker and Eriksen. Earlier, Eriksen and Kane had gone close but the last word would belong to Perbet. It has often been said that Tottenham and Pochettino need to win a trophy. It will not come in this competition.