The world champions, who suffered a shock opening loss to Mexico, must avoid another defeat which could see them crash out at a World Cup group stage for the first time in 80 years.
"Mats Hummels will most likely not be able to play because he injured his neck in training yesterday and it has not improved until today," Low told reporters in Sochi on Friday.
"He has not trained and obviously there are still a few hours but usually these things do not improve considerably overnight and tomorrow we need fit players. I think it makes no sense (for him to play)."
A likely replacement for Hummels is Antonio Rudiger but Low said he would wait until tomorrow to see Hummels' condition.
Sweden are joint top of the group after beating South Korea in their opener, and victory over Germany would almost certainly see them advance to the knockout stage. Mexico, also on three, play South Korea in the other group match.
The opening defeat has sent shockwaves back home in Germany and Low said that was understandable.
"It was no doubt a painful defeat against Mexico. We made many mistakes but we have processed them, talked about them and trained to avoid them."
"There is absolute focus and concentration and tomorrow we must deliver. There will be a reaction (to the Mexico defeat)."
Low said forward Mario Gomez was likely to start but did not clarify if he would join Timo Werner in attack or if he would operate as a lone striker against the tall Swedish defenders.
Low, however, ruled out the team overhaul which many German fans have called for, saying trust for his players, many of them 2014 World Cup winners, had not been lost.
"Why should that be the case? The fundamental trust for these players, who have played for years on a good level, will not be destroyed with one game," the 58-year-old said.
"I have fundamental trust in them and questioning everything after one game would be fatal. It is us who have to show a reaction tomorrow and I am certain there will be one."
(Reporting by Karolos Grohmann in Vatutinki, editing Neil Robinson)
