He was unable to play in the lineup for the 2-2 draw with the Netherlands in Amsterdam on Tuesday because of a calf strain.
The Germany camp sent the 31-year-old back to his club in London before the start of the match.
"It's nothing serious. Unfortunately, the area is a bit problematic because it's the transition to the Achilles tendon at the bottom of the calf," Germany coach Julian Nagelsmann said on Tuesday.
Fuellkrug was left out as a precautionary measure to avoid long-term consequences for the striker.
"If something were to happen, it would be long-term. That's why we're not taking any risks," added Nagelsmann.
"He will have to take a few days off. He will not be playing in the Premier League at the weekend."
Fuellkrug was in the starting lineup for Germany's 5-0 Nations League win over Hungary in Duesseldorf last Saturday and scored the opening goal.
But he has yet to find the net for his new English club after three matches this season.