Portugal coach Fernando Santos said that Cristiano Ronaldo's availability is still in question for their closing Group H match against South Korea on Friday.
The 37-year-old Portugal captain missed Wednesday's practice and stayed at the gym to do recovery and specific exercises and, with his team already through to the knock-out stages, he could be rested against South Korea even if fit.
"I think it is 50-50 if he plays or not, we'll see," Santos said on Thursday.
"It will depend on if and how he practices today, if we see he is in good condition... There is a plan for if he is not available."
After wins against Ghana and Uruguay, Portugal are first in the group standings on six points and can secure top spot with a draw or a win. South Korea still have a slim chance of qualifying.
Santos confirmed that defender Nuno Mendes will miss the rest of World Cup after the player left the pitch in tears against Uruguay when he sustained a thigh injury.
"Unfortunately he is out but by his will he will stay with us. It was his desire, his club agreed, and he will start his recovery here. His enormous desire to stay with us reflects the state of mind of the whole squad," he said.
With Mendes, Otavio and Danilo injured, Santos said he expects to rotate part of his squad with a view to keeping some players fresh for their game in the last 16.
Portugal World Cup 2022 squad
Portugal announced their 26-man squad on November 10, which features a raft of Premier League players; City, United and Wolves are represented in triplicate, plus lone Fulham player, Joao Palhinha.
Goalkeepers: Diogo Costa (FC Porto), Jose Sa (Wolverhampton Wanderers FC), Rui Patricio (AS Roma)
Defenders: Diogo Dalot (Manchester United), Joao Cancelo (Manchester City), Danilo Pereira (PSG), Pepe (FC Porto), Ruben Dias (Manchester City), Antonio Silva (SL Benfica), Nuno Mendes (PSG), Raphael Guerreiro (Borussia Dortmund)
Midfielders: Joao Palhinha (Fulham FC), Ruben Neves (Wolverhampton Wanderers FC), Bernardo Silva (Manchester City), Bruno Fernandes (Manchester United), Joao Mario (SL Benfica), Matheus Nunes (Wolverhampton Wanderers FC), Otavio Monteiro (FC Porto), Vitinha (PSG), William Carvalho (Real Betis)
Forwards: Andre Silva (RB Leipzig), Cristiano Ronaldo (Manchester United), Goncalo Ramos (SL Benfica), Joao Felix (Atletico Madrid), Rafael Leao (AC Milan), Ricardo Horta (SC Braga).
Who are the star names?
All-time leading international goalscorer Cristiano Ronaldo will look to add the World Cup to his horde of trophies. Ronaldo took the official player of the match award in the opening win against Ghana, but Rafael Leão was the top-rated player by Telegraph Sport readers, scoring a rating of 8.3.
Bruno Fernandes will also be one to watch, as will Rafael Leao, who has been impressing at AC Milan this season.
What are Portugal's results and fixtures?
November 24: Portugal 3 Ghana 2
November 28: Portugal 2 Uruguay 0
December 2: South Korea vs Portugal
What is Portugal's World Cup record?
Portugal have appeared at the tournament seven times. On their debut appearance in 1966 they recorded their highest ever finish: third place.
Portugal have appeared at the previous five editions of the World Cup and fell in the round of 16 at Russia 2018 when they were beaten 2-1 by Uruguay.
Argentina | Australia | Belgium | Brazil | Cameroon | Canada | Costa Rica | Croatia | Denmark | Ecuador | England | France | Germany | Ghana | Iran | Japan | Mexico | Morocco | Netherlands | Poland | Portugal | Qatar | Saudi Arabia | Senegal | Serbia | South Korea | Spain | Switzerland | Tunisia | Uruguay | USA | Wales
In what is sure to be Cristiano Ronaldo's last World Cup, can he win the Golden Boot? Find the latest top scorer odds here
Portugal are currently a best price of 11/1 to win the World Cup 2022.