Werder Bremen announced on Thursday they had cancelled training after an unnamed squad member tested positive for coronavirus, disrupting preparations for this weekend's league game against Hoffenheim.
The player concerned, who has been place in home quarantine, is "doing well and has no symptoms," Werder said in a statement.
Werder's first-team squad and Florian Kohfeldt's coaching staff are in individual voluntary isolation before the club's next round of testing for Covid-19 on Friday.
There are concerns whether Werder will be able to host Hoffenheim on Sunday (1700 GMT) behind closed doors in the Bundesliga.
The local health authority in Bremen has also said two of the Werder squad - an unnamed staff member and player - must also go into a 14-day quarantine despite both returning negative tests.
Werder are the latest German top-flight side to reveal positive tests for Covid-19 after Bayern Munich's Germany winger Serge Gnabry was sidelined by the virus Tuesday.
Germany reported a jump in Covid-19 figures on Thursday with 11,287 new cases in the past 24 hours -- a large increase from the previous record of 7,830 last Friday.