German was placed on administrative leave Thursday under the joint MLB-MLBPA domestic violence policy and was also placed on the restricted list. Under the policy, a player can remain on leave for up to seven days unless the league and the players' union agree to an extension.
The right-hander is under investigation for allegedly slapping his girlfriend at some point between late Monday night and early Tuesday morning.
German, 27, could face a significant suspension, major-league sources told Andy Martino of SNY.
No official announcement about German's status has been made by the league or the Yankees.