A record-breaking defeat to Germany on matchday two leaves Portugal with work to do against France in a repeat of the previous European Championship final.
Portugal became the first defending champions to concede four goals at the Euros and now need at least a point to reach the last 16.
Top spot in Group F could still be theirs if they beat France, although Portugal's Euro 2016 final triumph was their only win against Les Bleus in 13 attempts.
Reflecting on the Germany match ahead of this tough test, coach Fernando Santos said: "We all felt disappointed on our way back.
"Everyone feels a sense of responsibility, and the following day the players reacted well.
"They are experienced players and appreciate that sometimes you don't win. There are times when even the top teams don't deal well with defeat."
France have never previously played Portugal before the semi-final stage of a major tournament, but their meetings tend to be low scoring. The previous four have provided only three goals.
Although Didier Deschamps' men are already through as at least one of the four best third-placed sides, the coach insists they do not lack motivation.
"To be honest, in the situation where we are now, if we had six points I would have the same thoughts because a negative result would have the same impact," he said.
"We have the insurance of being qualified already, that gives us some kind of tranquillity but it won't change our playing style.
"Of course we owe it to ourselves and the French people to deliver the best possible result."
PLAYERS TO WATCH
Portugal – Cristiano Ronaldo
When is Ronaldo not Portugal's player to watch? He has history in his sights, too, having tied Miroslav Klose as the leading scorer at Euros and World Cups combined (19 goals) and moved within three of Ali Daei's world-record 109-goal tally last time out. The Juventus superstar has never scored against France, though, his six goalless appearances his worst record in international football.
France – Antoine Griezmann
Griezmann was the subject of praise from Santos ahead of this match and is himself only three goals adrift of a benchmark for France. He has 11 goals at major international tournaments, with Michel Platini's 14 leading the way. He has Thierry Henry (12) and Just Fontaine (13) to leapfrog before reaching that record, though.
KEY OPTA FACTS
– This is the fifth match between Portugal and France at a major tournament, but it is the first time they have met in the group stages; all four previous encounters took place in the semis (Euro 1984, Euro 2000, World Cup 2006) or final (Euro 2016). France won the first three while Portugal came out victors in the Euro 2016 showpiece match.
– Following their 1-1 draw with Hungary on MD2, France have avoided defeat in more matches when trailing at half-time than any other team in European Championship history (six – W4 D2).
– France are unbeaten in each of their past 11 group stage games at major international tournaments (World Cup and Euros), winning seven and drawing four. However, each of their past three MD3 group games in these tournaments have ended level (D3).
– Last time out versus Germany (4-2), Portugal became the first reigning champions in European Championship history to concede four goals in a single match in the competition. Indeed, Portugal had never conceded four goals in a single European Championship match before facing Germany on MD2.
– Portugal have lost two of their past three matches at major tournaments (World Cup and Euros), one more than they had lost in the previous 17 such games combined (W8 D8 L1). They last lost consecutive such matches within a single tournament at Euro 2008.