Cacau picked up the injury in training last week and was replaced by Miroslav Klose in their 4-1 win over England. Klose is expected to win his 100th cap on Saturday in Cape Town.
"Apart from Cacau, all other players are participating in training. He is doing some light running and therapy. But today and tomorrow it will not happen (training with the team)," coach Joachim Low said.
"So he is also doubtful for the weekend. The final decision will be taken on Friday," Low said.
Striker Lukas Podoloski broke off training in the afternoon but team officials said it was purely a precautionary measure after he complained of a minor muscle problem.
The 25-year-old is expected to play on Saturday.
While heaping praise on the Argentine team, Low said they were not invincible.
"I expect an unbelievably tight match as we cannot allow ourselves any mistakes because for any mistake we make, they will punish us in an ice-cold way. They are the top favourites for the World Cup. They have so many players able to score."
BALLACK RETURN
Low, who will have the support in the stands of German Chancellor Angela Merkel as well as former captain Michael Ballack, who was injured weeks before the tournament and had to drop out, said Argentina did also have some weaknesses.
"Argentina can be hurt," he said. "We have found some details of their weaknesses but I am not going to elaborate on that."
He also said he was not yet preparing for a penalty shoot-out. Germany beat Argentina on penalties in the quarter-finals at the World Cup four years ago.
A small note detailing which side the Argentina penalty-takers usually picked was given to then Germany keeper Jens Lehmann and was largely credited with helping him save two spot kicks and send them through to the semi-finals.
"If we needed a note in 2006 for the penalties this time we need a whole catalogue if you see the quality of players they have in the squad," Low said.
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