Cristiano Ronaldo's Portugal will be fighting to keep their World Cup campaign alive when they play the United States in Sunday's key match.
But after a 4-0 defeat by Germany in their opening Group G match, images of Ronaldo training with an ice pack on his knee have further worried Portugal's fans.
Portugal take on United States, who beat Ghana 2-1 on Monday, in Manaus at 2200 GMT. In Group H, Belgium play Russia in Rio de Janeiro at 1600 GMT while South Korea take on Algeria in Porto Alegre at 1900 GMT.
Portugal's coach Paulo Bento did not say whether Ronaldo would play. But he bemoaned the fact that four others -- the suspended Pepe and injured full back Fabio Coentrao, forward Hugo Almeida and goalkeeper Rui Patricio -- would be missing.
"The situation is very simple: either we win or we start to pack our bags," said Bento.
"It is not a scenario that the Portuguese are used to," he added.
US coach Jurgen Klinsmann will be without striker Jozy Altidore who has a hamstring injury. Clint Dempsey, who scored the first goal against Ghana, is likely to wear a protective face mask after breaking his nose in the first game.
-- Blunder goalkeeper --
Belgium play Russia at the Maracana stadium in the decisive Group H encounter. Belgium, who beat Algeria 2-1 on Tuesday, can reach the second round with a game to spare if they win. Russia would almost certainly be out if they lose.
Russia's coach Fabio Capello insisted he would stick with goalkeeper Igor Akinfeev for the game despite his costly blunder against South Korea.
Akinfeev fumbled a shot by South Korea's Lee Keun-Ho into his own goal on Tuesday. Russia had to fight back to scrape a draw and Capello now faces mounting criticism for the performance.
"I had decided after the mistake that Akinfeev would stay because he's a great goalkeeper," the Italian coach said. "I never thought about changing him. He's one of the best in the world."
Capello said he expected a lot of pressure on Akinfeev from Belgium in Sunday's game. Belgium have "surprised all of Europe," he added.
Belgium's captain Vincent Kompany was confident he would shake off a groin strain to play. Coach Marc Wilmots said he expects Russia to press for goals.
"The advantage for us is that we don't need to take the match in hand. It's up to Russia to do it," said Wilmots.
Algeria go into their Porto Alegre match with South Korea still desperate to end a run of seven games at two World Cup finals without a win. Another defeat will spell the end of this adventure for the Desert Foxes.
"Now is not the time for crying, this match is decisive," said coach Vahid Halilhodzic.
South Korea have reached the knockout stages twice in eight appearances at the finals, including their giant-killing run to the semi-finals in 2002.
South Korean coach Hong Myung-Bo, captain of the 2002 side, expects Algeria to be more attacking against his team than they were against Belgium.
"I can't predict the result," said Hong. "But what I can say is that we're going to play to win, because we absolutely have to win to hope to reach the next round."