Rangers could turn Benfica's Estadio da Luz into a seething cauldron of hate if they score first because the home fans will turn on their own players, according to their ex-director of football. 

And another Benfica legend believes under-fire manager Roger Schmidt will lose his job if they crash out of the Europa League to Rangers.

Rangers face the Lisbon giants in tomorrow's Round of 16 first leg showdown.

But German boss Schmidt has faced a barrage of criticism after his men were pummelled by Porto in a 5-0 hammering, coming just days after they lost the first leg of the Portuguese Cup semi-final first leg to bitter rivals Sporting Lisbon.

Schmidt has faced hostility for refusing to apologise to their fans after the capitulation with president Rui Costa wheeled out instead to say sorry to their supporters.

And former player and ex-director of football Gaspar Ramos believes it will turn nasty in the home leg if Philippe Clement's side take the lead.

He said: "If we lose the first goal against Rangers, it will create an incredibly toxic atmosphere.

"A Rangers goal would have disastrous consequences for the team because of the reaction of the fans.

"Look, that game at Porto was humiliating for us.

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"Roger Schmidt should apologise to the Benfica fans, in particular, and to the entire football world for having played such pathetic football.

"I am afraid the manager has not faced reality for a long time. He always seems to see different games than the ones we watch.

"The fact is Benfica have the best squad in the league...and the worst manager.

"I am afraid the president must take responsibility too. He extended the contract of the manager when many of us were against it."

And Benfica's former vice-president, Jose Manuel Antunes, believes a Rangers win will spell the end for Schmidt.

He said: "If Benfica go out of Europe to Rangers, I cannot see how Roger Schmidt could stay on.

"It's not just a win he needs against Rangers, it has to be a convincing one.

"He's already under extreme pressure after the disgrace of Sunday.

"Everyone can see Benfica have a far better squad than Porto - they should beat them every single time they play.

"It is incomprehensible that there was such a disaster. It was a defeat that was shameful for the Benfica nation.

"Then refusing to apologise shows he doesn't understand the culture of the club. That worries me, he’s been here for a year and a half and he should understand a little better.”