Hummels scored a goal in Germany's 4-0 opening win over Portugal but hurt his right thigh in the match and hasn't been able to train with the team since.
Germany coach Joachim Lowe said Hummels was able to run on Thursday but did not tackle or take part in the full practice.
Loew is waiting to see how Hummels reacts to the team's last practice Friday before deciding on his lineup.
Hummels went through the usual warm-up routines at the Arena Castelao but reporters were ushered out after 15 minutes and could not see if he participated in the full session.
Defensive midfielder Sami Khedira said it was always difficult to make changes in the defense.
''If Max Hummels can't play that would be a pity, especially if we might have to change the defense and that is always difficult for the coach. But we do have other excellent players,'' Khedira said.
If Hummels is ruled out, Jerome Boateng may move from right back to the central position. Loew did not say who would take the position on the flank, but added, ''we have options.''
Shkodran Mustafi is also being considered as a central defender.
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