Tottenham Hotspur 2,Gent 2 (Aggregate 2-3)
Tottenham manager Mauricio Pochettino rallied behind Dele Alli despite the midfielder's sending off contributing to their shock Europa League exit at home to Gent.
Spurs chased two goals in vain with 10 men for 50 minutes, after Harry Kane's own goal nullified Christian Eriksen's opener and Alli was expelled for a dangerous lunge.
Victor Wanyama's strike put them in touching distance of a famous comeback, but instead the curse of Wembley struck Spurs again and substitute Jeremy Perbet clinched a last-16 spot for Gent.
"He is very disappointed, he is sad. He knows he made a mistake. But in football it happens," Pochettino said of Alli.
"It's only a year and a half that he's playing for Tottenham and in the Premier League. All he has achieved in a very short period is because he's a special player, a special boy.
"He has an unbelievable personality and character. For that he's a great player but in the same way he is how he is. Now is the time to give support to him because he is very disappointed, very sad."
Gent coach Hein Vanhaezebrouck admitted his team had ridden their luck in the second leg.
"I should apologise, but if you win do you have to apologise? That is the question," said Vanhaezebrouck.
"In my point of view, yes, because I'm a coach who likes to play football and win games we deserve to win. In the point of view of my fans, players, directors I should not apologise because we have taken out Tottenham over two games.
"Today we were not good. But in the first game we were. If Tottenham lost this one, it's not here, it's in Gent."
Pochettino rotated his squad minimally in a busy fortnight and made just four changes from Sunday's FA Cup win at Fulham, with Kane, Alli and Toby Alderweireld making their fourth starts in just 13 days.
Sluggishness was not in evidence initially as Tottenham started like a team bent on overturning their first-leg deficit.
Eriksen capitalised on Rami Gershon's misjudgment of an Eric Dier long ball to slot through goalkeeper Lovre Kalinic's legs, while Alli and Kyle Walker both fired off target as Spurs sought to add to their lead.
But sloppiness crept into their play. Kane glanced into his own net when the hosts failed to clear a corner and Gent caused more panic in the box with another set piece.
Tottenham now needed two more goals and, with Kane looking jaded, were restricted to long-range efforts.
An uphill task turned mountainous when Alli saw red for a wild, high challenge on Dejaegere just before half-time.
Kane fluffed two opening soon after the break but Wanyama gave Spurs hope on the hour when he collected Eriksen's disguised lay-off and planted a high shot into the far top corner from 18 yards.
Tottenham sensed a third and substitute Heung-Min Son's trickery threatened to provide it, but Gent rode the storm and delivered the killer blow eight minutes from time when Perbet poked home after lax defending from Dier.
Pochettino's slim hopes all but vanished when Son blazed over when sent clear by Kane, and the Spurs boss illustrated the extent of his faith in misfiring forward Vincent Janssen by waiting until the 89th minute to thrust him into action.