Portugal were hammered 4-1 by Denmark on Saturday, an embarrassing Nations League defeat in their first match without Cristiano Ronaldo following his retirement from international football.
Rasmus Højlund starred with a superb double as Denmark moved into second place in Group A4 and closed in on a spot in the quarter-finals with an exceptional display in Braga.
Denmark 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 will see Denmark through.
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 No 7 and his name on their jerseys.
Denmark were the better team from the first minute and it was no surprise when the visitors took the lead from Pierre-Emile Højbjerg's penalty in the 43rd minute.
Højlund lashed home a volley four minutes after the restart and seven minutes later left the home crowd were stunned after the Napoli striker skipped past Rúben 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.
Wales suffered a 3-1 defeat to Norway in Oslo to dent their hopes of staying in the top tier of the Nations League.
Antonio Nusa and Andreas Schjelderup struck in the space of nine second-half minutes as Norway turned the screw. Substitute David Brooks halved the deficit 11 minutes from time as Wales finished strongly.
However, Connor Roberts brought down Schjelderup and Erling Haaland converted from the penalty spot, extending his Nations League goals record to 23, as Norway avenged their October defeat in Cardiff.
It means Wales will definitely finish bottom of Group A4, irrespective of Tuesday's result at home to Portugal.
Although they could finish on six points with Norway, they have a worse head-to-head record and could now face a playoff in March to avoid relegation to Group B.
Terry Devlin's first international goal kept Northern Ireland top of their Nations League group as a 1-0 win over Ukraine set up a promotion decider away to Hungary on Tuesday.
The 23-year-old Devlin has been in the goals for Portsmouth this term with four, and opened his Northern Ireland account with a fine strike in the 68th minute as he left the Ukraine goalkeeper Anatoliy Trubin flat-footed with a shot from distance.
Pierce Charles then made a superb save to deny Danylo Sikan and preserve Northern Ireland's fifth consecutive clean sheet – the first time they have achieved that since 2017 – and ensure they remain the only side in the competition yet to concede.
The victory put Northern Ireland back on top of Group B2 after Hungary's 2-0 win over Georgia earlier in the afternoon, and ruled Ukraine out of contention as they lost three successive matches for the first time in six years.
A draw in Budapest would be enough to elevate Michael O'Neill's team to League A, while even in defeat they would face a playoff in March, and they have also earned a pot two place in next month's Euro 2028 draw.
However, O'Neill will need to watch Tuesday's match from the stands as he joined Jamie Donley – who had a first-half strike ruled out for offside – in earning a late yellow card that results in a suspension.
