Portugal were hammered 4-1 by Denmark on Saturday, an embarrassing Nations League defeat in their first match without Cristiano Ronaldo following the superstar forward's retirement from international football.
Rasmus Hojlund starred with a superb brace as Denmark moved into second place in Group A4 and closed in on a spot in the quarter-finals with a brilliant display in Braga.
The Danes are on nine points from five fixtures, three behind Portugal who were already sure of qualification for the last eight having won all four of their previous group fixtures.
A draw against third-placed Norway on Tuesday, 3-1 winners over Wales earlier, will see Denmark through while Portugal hope that Saturday's disaster isn't a sign of things to come.
"There are no nights to forget; it was a night of learning, of seeing the mistakes we made," said Portugal midfielder Bruno Fernandes.
"Denmark were also very clinical -- they scored from the chances they had and it was a match where things ultimately went wrong for us."
Ahead of kick-off Portugal paid tribute to Ronaldo, who announced his exit from the international game last week, with the team and mascots walking out wearing Ronaldo's number seven and his name on their jerseys.
Fans held up a huge banner which read "Thank you captain" as the teams entered the field, while applause rolled around the stadium once the match clock hit seven.
Ronaldo made his debut for Portugal in 2003 and went on to establish world records for goals and appearances in international football, netting 146 times in 234 matches.
The highlight of his international career was winning Euro 2016, but it ended badly when the 41-year-old fell out with Portugal coach Jorge Jesus over not being selected for a Nations League fixture in September.
That row led to the five-time Ballon d'Or winner being handed a 30-day suspension by the Portuguese football federation and his subsequent retirement, and Portugal looked like they needed prime Ronaldo in a dismal display.
Denmark were the better team from the first minute and it was no surprise when the away team went in at the break thanks to Pierre-Emile Hojbjerg's spot-kick in the 43rd minute.
Hojlund lashed home a brilliant volley four minutes after the restart and seven minutes later left the home crowd shell-shocked with a strike of which Ronaldo would have been proud, the Napoli striker skipping past Ruben Dias before crashing home a powerful shot from the edge of the area.
Boos and whistles began to ring out at the Estadio Municipal when Joachim Andersen headed in the fourth, and Bernardo Silva's late consolation effort barely dampened the discontent.
"Every single Denmark player put in their best performance I've seen in a long time. Even the substitutes, which made for a fantastic overall display," said Morten Hjulmand.
"We scored some great goals and we deserved to win."
Antonio Nusa opened the scoring for Norway just before the hour mark in Oslo with a fine low strike before Andreas Schjelderup tapped home a perfect low cross from Erling Haaland, who rounded off the scoring from the penalty spot two minutes from time.
Wales briefly had hope of getting a result when David Brooks' chipped finish halved the deficit in the 79th minute, but Craig Bellamy's team will finish bottom of the group and risk being relegated to League B.
Northern Ireland meanwhile need a point from their final Group B2 match in Hungary on Tuesday to be promoted to League A for the first time after a 1-0 win over Ukraine secured