The 25-year-old playmaker, who plays a key role in their young squad with the absence of injured captain Michael Ballack, picked up a thigh muscle injury in their final Group D match against Ghana.
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He has missed the team training for the past two days.
Defender Jerome Boateng is also doubtful following his calf muscle injury in the same game. Both players trained lightly on Saturday.
"We will take the final decision tomorrow and the last training where we will see how fit they are," said goalkeeping coach Andreas Koepke, who replaced coach Joachim Low at the final pre-match news conference on Saturday.
"Both players will undergo a test tomorrow to see in what condition they are because it does not make sense for them to play if they are not 100 percent," said Koepke.
Loew has said 20-year-old midfielder Toni Kroos, who came on as a substitute for Schweinsteiger late in the Ghana match, could replace him from the start.
Marcell Jansen or Holger Badstuber could replace Boateng as left-back.
"All the other players have been training superbly so it all will be decided tomorrow," Koepke said.
Striker Cacau, however, will definitely miss the game with a stomach muscle injury picked up in training on Friday. Koepke said he would be out for up to four days.
