It was business as usual at Yankee Stadium on Thursday as the team prepared for an evening game against the Los Angeles Angels. Then, at 1:36 p.m., Major League Baseball announced that Yankees pitcher Domingo German had been placed on administrative leave under its domestic violence policy — a precursor to a larger investigation and a possible suspension just days before the postseason.
Within hours staff members were removing issues of Yankees Magazine, which had German on the cover, from the stands. German, who had pitched the night before, was barred from the stadium and from speaking with team officials during the leave.
Administrative leave can last up to seven days — though it can be extended for further investigation — but the Yankees have carried on as though they will not have German, one of their most consistent starting pitchers, for the rest of the regular season or for the playoffs.
In fact, according to two people familiar with the case who requested anonymity to discuss details of an active investigation, German is unlikely to pitch again this year. The Yankees claimed a spot in the playoffs on Thursday by winning their first division title since 2012.
M.L.B. investigators are looking into an incident involving German, 27, and his girlfriend, with whom he has at least one child, at his residence in Yonkers, where she also lives during the season, one of the people familiar with the case said.
The incident that led to the inquiry, which was not witnessed by anyone else, happened either late Monday night or early Tuesday, the person said. German and his girlfriend were seen Monday night at a gala held by Yankees pitcher C.C. Sabathia and his charity at The Shed at Hudson Yards in Manhattan.
M.L.B. was informed of the incident through a chain of people who had heard about it from German’s girlfriend, the person said. The police have not been involved so far, but M.L.B. officials put German’s girlfriend in touch with domestic violence experts, the person said.
The absence of a police report makes German’s case unusual; most similar administrative leaves in M.L.B. have come after an arrest. So far, the case appears to have been handled entirely by M.L.B., and it is unclear how much the Yankees knew about the investigation before German pitched two and one-third innings in a loss to the Los Angeles Angels on Wednesday night.
Yankees Manager Aaron Boone said that he learned of German’s administrative leave during his drive to Yankee Stadium before Thursday’s game, but he added that he had previously heard “whispers” of an M.L.B. investigation.
“It was vague to me,” he said. “All I knew was Major League Baseball was involved in an investigation.”
M.L.B. began conducting a preliminary inquiry on Tuesday afternoon. The league was still conducting interviews, including with people connected tothe Yankees, leading up to Wednesday’s game, the person said.
When Yankees officials spoke with M.L.B. headquarters, they were told to conduct team business normally, including with German, since the domestic violence policy put the matter in the league’s jurisdiction, both people with knowledge of the case said. The policy was established by M.L.B. and the players’ union in 2015.
Preliminary investigations into domestic violence accusations do not always yield enough evidence to trigger administrative leave. According to the collective bargaining agreement, an administrative leave is not considered disciplinary on its own. And if German, who had previously been told he was going pitch on Wednesday, had been held out of the game, that decision could ultimately be considered disciplinary. Altering the plans for German could also have led to his becoming aware of the inquiry earlier than M.L.B. wished, said one of the people familiar with the investigation.
It wasn’t until close to 10 p.m. on Wednesday, after German had pitched, that M.L.B. decided it had enough evidence to place him on administrative leave, said one of the people with knowledge of the investigation. The Yankees and the players’ union — which declined to challenge German’s placement on leave — were officially informed on Thursday.
German did not respond to attempts to reach him by telephone and text message on Friday.
On the field, the Yankees must factor German’s uncertain status into their already complicated pitching plans for the playoffs, which will begin for them on Oct. 4 with an American League divisional series.
German led the Yankees with an 18-4 record, and he had a 4.03 earned run average through a career-high 143 innings. He was expected to fill a versatile role come October, possibly both starting and pitching in relief.
Without German, Boone said, “it’ll be a little bit of everyone.” He said the Yankees’ choices would depend on the number of pitchers they elect to carry in the postseason and which opponent they are facing.
Because their pitching strength is in their bullpen, the Yankees were already planning to be creative in their approach, shuffling pitchers to roles different from usual.
In addition to most likely being without German, the Yankees must handle their most talented starting pitcher, Luis Severino, with care as he builds up his workload. He made his season debut on Tuesday after dealing with injuries all year.
Another factor: The Yankees must evaluate how Sabathia, 39, who has a 4.99 E.R.A. this season as a starting pitcher, handles coming out of the bullpen over the final week of the regular season, in preparation for a possible relief role in October.