Brazil goalkeeper Marcos was injured in a practice match on Monday, 48 hours before the World Cup semi-final against Turkey.
Marcos went up for a corner in a game between the first team and the reserves and appeared to over-stretch himself.
He lay on the pitch for two minutes before being helped off to the sidelines. He was taken to the dressing rooms, supported by two men, and appeared unable to put weight on his right foot.
Earlier on Monday, Marcos was named in the 33-man short-list for FIFA's All-Star team of the finals.
Brazil striker Ronaldo is continuing to recover from a thigh injury but is still doubtful for the World Cup semi-final against Turkey on Wednesday, according to team doctor Jose Luis Runco.
Ronaldo, who was substituted in the quarter-final win over England on Friday, played in a practice match between the first team and reserves on Monday without feeling pain before quitting the session after half an hour.
"He did what we agreed before hand," team doctor Jose Luis Runco said. "He didn't feel anything. We will see his reaction tomorrow. We are going to look at his reaction day by day.
"He didn't do any sprints, just as we had agreed before."
But asked if Ronaldo, who has scored five goals in five games at the finals, could be confirmed for the semi-final, Runco said; "Not yet.
"I'm not worried about this now. I want to see it day by day. He didn't feel any pain before the game and he didn't complain afterwards.
"If he doesn't complain tomorrow, he can train with more intensity."
Ronaldo was more keen to talk about his bizarre new haircut -- he has shaved most of his hair off except for a small lump at the front of his head -- than his aching muscles.
"I've got another day to relax but I believe I can be ready in time," he said of his thigh. "(The haircut) is something new, something personal, there's nothing special about it.
"I cut it myself. It's that bad, is it?"