Rangers' Europa League dream took a damaging but not yet fatal blow as they were beaten in Braga.
Giovanni van Bronckhorst 's side were left with work to do in the hunt for a semi-final place after Abel Ruiz' first-half goal won a tight contest.
Anticipation for a mammoth occasion in the club's history was dampened by a devastating defeat to Celtic in the Premiership title race at the weekend.
And the Ibrox side were not their usual vibrant continental selves at the Estadio Municipal de Braga.
They failed to fashion an opportunity of note and were undone by the same slack defending which allowed their city rivals to pull clear domestically on Sunday.
Rangers now face another monumental evening at Ibrox as they bid to rescue their quest to reach the last four.
Van Bronckhorst drafted Glen Kamara, Scott Arfield and Fashion Sakala into his side, the latter playing through the middle following the news Alfredo Morelos' season is over.
And it was the visitors who threatened first, with Sakala snatching at a rebound after Kent had been played in and denied by a swarm of red and white shirts.
The pace of that pair was clearly spooking Braga and Rangers had the better of the opening exchanges without troubling Matheus in the home goal.
But despite that threat, they came within a whisker of going behind before the half-hour mark.
Rangers failed to deal with a deep cross and the ball broke to Horta to slam against the post with the goal at his mercy.
Horta did have the ball in the net a minute later, but the goal was ruled out for a foul on Ryan Jack in the build-up.
Nevertheless, it was a warning for Rangers as they barely escaped a sloppy spell without punishment.
It was one they did not heed.
Again it was woeful defending - Leon Balogun taking a swing and a miss at a loose ball to allow Ruiz to control and fire past Allan McGregor.
Rangers could hardly claim Braga did not deserve the advantage and it was one they sought to press home after the break.
Yan Cuoto was particularly effervescent on the right flank but the visitors, to their credit, saw out an early second-half push to re-establish a presence again.
The problem was, it was a rather benign one.
It took the introduction of Kemar Roofe, Joe Aribo and Borna Barisic to build some forward momentum as Rangers finally began to push forward with purpose.
They could well have equalised from a corner had Connor Goldson directed his free header on target from an admittedly tricky angle.
He then laid off for Calvin Bassey from another set-piece but his strike was blocked by Braga bodies putting themselves on the line and it proved to be the visitors' final chance.
On the line, as a matter of fact, is where Rangers must now lay it all next week.
5 talking points
The dream on a knife edge
Rangers tend to only participate in blockbusters in this tournament but there were all too few signs of a spark on this occasion.
A Goldson header aside, it's difficult to immediately recall any clear cut chances for Van Bronckhorst's side.
As it was against Celtic, there was plenty of endeavour but too little invention from the men in Light Blue. As time progressed,
The outcome is that their Europa League dream has been left on a precarious knife edge ahead of next week's return leg at Ibrox.
Rangers at home in this competition, however, means you can never rule them out and they could give the home crowd that blockbuster their travelling fans were denied here.
Gio's changes don't deliver
The Ibrox boss said ahead of kick-off he was putting trust in the depth of his squad as Aribo, Roofe and Ramsey made way for Arfield, Kamara and Sakala.
Trusting in depth was at odds with how Van Bronckhorst used only two subs from a possible five in defeat to Celtic and it was the same pair who came off the bench there who started here, with the addition of Kamara into midfield.
The omission of Ramsey, who was a positive at Ibrox on Sunday, was notable - especially considering how quiet Kamara was.
Sakala, too, didn't look particularly comfortable as a central striker and despite threatening in behind early on, couldn't make a significant mark on proceedings.
Defending costs Rangers again
Rangers gave away two dreadful goals against Celtic and they were just as bad here.
They were given a stern warning when Horta's goal was ruled out by VAR, but the standard of defending suggested it wouldn't be long until they made one count.
Balogun's mistake was a bad one, although admittedly it was very ruthlessly punished.
But if you continue to make such mistakes then you can only expect to pay.
It's all a far cry from the Rangers defence which gave so little away last season.
Impressive Braga
The last time these sides met there was a real Jekyll and Hyde feel about Braga.
They were excellent for much of the first leg before being swept up in the Ibrox cauldron and then were mostly all over the place in the return leg.
And despite Rangers starting on the front foot here, Carvalhal's side grew and grew into proceedings.
Yan Couto at right-back, who very nearly joined Celtic in the summer, was particularly impressive down the flank, causing Rangers all sorts of issues.
An odd feeling for a huge occasion
For what was, realistically, the biggest night in the club's history since 2008, there was a somewhat muted feeling around this all-important 90 minutes.
That was, of course, because of what happened at the weekend.
Europe is monumental to the club but the pain of all-but giving up their Premiership title cast a shadow over the build-up, with as many pre-match questions still centring on defeat to Celtic as the prospect of beating Braga.
That cloud darkened further when Braga deservedly took the lead before half-time, with Rangers leaving it until late in the second period to mount a meaningful charge.
And although it proved fruitless, there's still everything to play for in this tie.
