The Yankees pitcher, who is currently second in the majors in wins with 18, has been suspended for seven days, "barring an extension," according to the league.
The 27-year-old from the Dominican Republic has been a surprise star for the Yankees this season and carries a league-leading 18-4 win-loss record. He has a 4.03 ERA and 1.15 WHIP in 123 innings pitched.
The Yankees currently have the second-best record in baseball to the Houston Astros and German was expected to get a postseason start. He pitched 2 1/3 shutout innings Wednesday night, just hours before his suspension.
Now, his 2019 future is unclear.
"We’ll wait and see what ultimately comes down, but we have to certainly make plans," Yankees manager Aaron Boone said of German's postseason availability at a pregame press conference Thursday. "He may not be a part of it."
The Yankees issued a statement in agreement with the suspension, saying, "We fully support all measures being undertaken by the Commissioner’s Office pursuant to the Policy on Domestic Violence. We support this policy which reinforces that domestic violence has no place in our society and cannot be tolerated. We have followed the lead of Major League Baseball and will continue to provide our complete cooperation throughout the investigative process. We reserve any further comment until the investigation reaches its conclusion."
MLB is still investigating the incident and released no details.
"MLB Department of Investigations has commenced an investigation into the matter that led to his placement on Administrative Leave," the league said. "MLB will have no further comment until the investigation is complete."
Boone said he had yet to speak to the team about the incident, but he'd "get up there and talk as a group, as a family, and speak from the heart about it."
"Set baseball aside," Boone said. "This is a bigger issue obviously and something that, you know, when you hear the words ‘domestic violence’ it’s one of those things that stops you in your tracks."
The Yankees are currently in position to face either the Minnesota Twins or Oakland Athletics in the first round of the playoffs with nine games left to play.
"There's denying the importance of Domingo to our team," Yankees manager Aaron Boone said at a pregame press conference Thursday. "So there is that element of we must continue on and continue to press forward."
The Yankees host the Los Angeles Angels of Anaheim Thursday night.
ABC News' Darren Reynolds contributed to this report.