After overcoming injuries to key players from spring training to the final two weeks of the season on the way to an AL East title, the Yankees’ postseason hopes took a colossal dip Thursday due to something a lot more serious than a strained oblique.

Major League Baseball announced Thursday that 18-game winner Domingo Germán was placed on administrative leave under the joint MLB-MLBPA Domestic Violence Policy.

The alleged incident being investigated happened Monday night, two nights before Germán worked 2 ¹/₃ innings in the 3-2 loss Wednesday to the Angels at Yankee Stadium. ESPN.com reported on Friday that German would not pitch for the Yankees the rest of the season, including the playoffs.

Germán will get paid while on leave, but not if he is disciplined. He is making $557,500 this year.

Asked about Germán’s status before Thursday night’s division title-clinching win over the Angels, manager Aaron Boone said his staff has to be prepared for not having Germán for the postseason.

“I’ll guess we’ll wait and see what ultimately comes down, but we have to certainly make plans like he may not be a part of it and that way when you’re talking about plans for postseason, and things like that, it does turn into like losing a player to injury or whatever,’’ Boone said. “So it’s part of the pie that we’re dealing with as we move forward and making evaluations and determinations and formulating our roster and things like that. And this is another piece to that.”

Losing the 27-year-old might be the biggest loss to a team that has had many of them and survived to this point. The versatile right-hander started 24 games, and in his past two outings, Germán followed CC Sabathia and provided multiple innings out of the bullpen. Though the Yankees haven’t announced their postseason rotation plans, Germán figured to be a big part either as a starter or a reliever. In 27 games, Germán is 18-4 with a 4.03 ERA.

Though James Paxton, who has won his past nine starts, is a prohibitive favorite to start Game 1 of the ALDS no matter who the opponent is, the rest of the rotation is in flux. Thursday night’s starter, Masahiro Tanaka, along with Luis Severino, who has made one start this season, J.A. Happ and Sabathia are in the mix, though Sabathia could make the postseason roster as a reliever. And the Yankees haven’t closed the door to using a reliever such as Chad Green to start a postseason game.

“There’s no denying the importance of Domingo to our team, so there is that element of: We must continue on and continue to press forward,’’ Boone said. “But it’s also this is something that touches our society, unfortunately. So hopefully that’s a forum for players to talk through it or have comments or questions or whatever, and there’s no script you go off for this. So you just as best you can, deal with it, handle it and offer the right kind of support.’’

Boone addressed the players with general manager Brian Cashman before Thursday night’s game.

“Candid, you know it is a difficult situation,” Boone said of his message. “None of us know that many details. You just try and play it out. Sometimes things come up during the course of the season that you are not necessarily prepared for. Just try and talk through it the best you can.’’

The Yankees found out Tuesday they wouldn’t have Dellin Betances (Achilles tendon) for the postseason. Aaron Hicks (elbow) isn’t likely to make it back no matter how deep the Yankees go. Gary Sanchez (groin) might not make it back for the first round of playoffs. Giancarlo Stanton played in his 11th game of the season as the DH on Thursday.

And yet the biggest obstacle to the Yankees’ dreams of winning the World Series is the possibility that Germán, perhaps their most valuable pitcher, won’t be able to help.