Portugal defender Nuno Mendes is set to miss the rest of the World Cup with a thigh injury, a federation source told AFP on Thursday.
The Paris Saint-Germain left-back is likely to be sidelined until late January.
Mendes missed Portugal's first game, a 3-2 win over Ghana, with muscular fatigue, but was injured during the 2-0 win over Uruguay on Monday.
The Portuguese federation said he suffered "a muscle injury in his left thigh" without specifying his expected recovery time but the source said he would not recover in time to play any further part even in the tournament.
Mendes will remain with Portugal's camp in Qatar despite his injury.
"He will continue to stay in Qatar, because the player wanted it, (PSG) allowed him to stay here with us," Portugal coach Fernando Santos told a press conference Thursday.
"This reflects the spirit of the team and how united we all are."
Borussia Dortmund full-back Raphael Guerreiro played the first match and replaced Mendes against Uruguay, and is in line to hold the position going forward.
Portugal, already qualified for the knockout phase, face South Korea on Friday, knowing only a point would guarantee them top spot in Group H.