Alli picked up a straight red card for a horror tackle on Gent's Brecht Dejaegere in the first half and the match finished 2-2, with Gent progressing 3-2 on aggregate after their 1-0 win in Belgium last week.

It was the first red card of the 20-year-old's career and came with the score at 1-1 after Harry Kane's own goal had cancelled out Christian Eriksen's opener.

Spurs looked on course for a memorable win after Victor Wanyama's fine strike left them needing one more goal to progress but Jeremy Perbet equalised to seal the tie.

Pochettino refused to blame Alli for the result, however.

"He is very disappoited and sad. In football, it happens. He knows he made a mistake," the Spurs manager told a postmatch news conference.

"Now he tries to move on and improve. In the future, we must avoid that [kind of] situation."

This time last year, Alli was lucky to pick up just a yellow card for appearing to stamp on Fiorentina's Nenad Tomovic and after the game in Italy Pochettino said he had "a lot to learn about elite football."

Reminded of those comments, the manager said: "It's difficult. That's not to justify him but it's a different action. [Today] he was fouled before, it was a clear foul. That's not to blame the referee but the action came in very soon, that tackle.

Dele Alli was sent off for a strong challenge in the first half of Thursday's Europa League draw.

"I think he deserved to be sent off. He knows. That kind of action can always happen.

"It's only one-and-a-half years he is playing for Tottenham in the Premier League, everything that he has achieved in a very short period is because he is special. A special player, a special boy. He has unbelievable personality and character.

"Before that, he is a great player. In the same way, he is how he is -- he is very passionate to play football and sometimes this action happens. Now it's time to support him, he is very sad and disappointed in the changing room."

Gent manager Hein Vanhaezebrouck also refused to blame Alli, even though Dejaegere limped off with a bloodied shin in the second half, still feeling the effects of the challenge.

"I don't think he did it on purpose but it was a red card -- it was really dangerous and we lost our player. This happens in football when teams go 100 percent in the duels, it's unlucky. I will not blame the guy. He went for the dual fully, he was too late and it was really dangerous," he said.

Pochettino was happy with his team's performance, saying the effort was "unbelievable," but stressed they needed to recover quickly for Sunday's Premier League home game against Stoke.

"It's key now to recover physically and mentally. On Sunday, a team that is very fresh arrives. Be sure they will be ready to fight against us. Now we move on and forget this competition," he said.

"We try to be focussed on Sunday and be ready to fight. The competition doesn't wait for you, the competition pushes you to try to give your best. Now is not time to cry, it is time to move on. Tomorrow we start to prepare the game against Stoke."