Norwich boss Dean Smith says Christoph Zimmermann "has a tough decision to make" about his Carrow Road future.
Zimmermann has twice helped Norwich to Premier League promotion since arriving from Borussia Dortmund II in 2017, but featured just five times last term.
"We've had a club who have asked the question about Zimbo and we've given him the opportunity to make a decision," Smith said.
Zimmerman has a year remaining on his deal with the Canaries, with an extra 12-month option on his contract also available.
Asked if Smith could reveal the name of the interested club, or confirm if Darmstadt had made the approach, Smith told BBC Radio Norfolk: "I can't say at the minute.