12:48 PM PT -- Yankees manager Aaron Boone just spoke with reporters ... and said he had heard "whispers" German could be placed on administrative leave earlier this week.
He added, "Set baseball aside, this is a bigger issue ... when you hear the words 'domestic violence,' it stops you in your tracks."
New York Yankees star pitcher Domingo German has been placed on administrative leave while Major League Baseball investigates allegations of domestic violence.
A source tells TMZ Sports the alleged incident happened earlier this week after the Yankees returned from their road trip in Toronto. We're working on more details.
For their part, the Yankees have announced they fully support the MLB's decision saying, "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."
Under MLB policy, German's stay on Administrative Leave can last up to seven days ... although the league has the power to extend that timeline.
German has been a stud for the Yanks this season, winning 18 games with 153 strikeouts in 143 innings.
The 27-year-old just pitched for New York at Yankees Stadium on Wednesday night ... throwing 2.1 innings and giving up just 1 hit and no runs.
He was expected to be relied on heavily when the Yanks kick off their run toward their 28th World Series championship this October.