C. C. Sabathia, a commanding presence and a key leader for the Yankees, if no longer a franchise star, left the team and said Monday that he was entering an alcohol treatment program.

Although Sabathia was not expected to pitch Tuesday night in the A.L. wild-card game against the Houston Astros — the Yankees’ first playoff game since 2012 — the announcement left the Yankees stunned. Many members of the team threw their support behind Sabathia.

“All that matters now is what’s happening now, which is obviously he’s going to get the help necessary in a structured environment,” General Manager Brian Cashman said in a news conference at Yankee Stadium, just before the team worked out. “He’s going to get professional help. That’s the most important thing right now.”

Cashman said that Sabathia had reached out to him, Manager Joe Girardi and other team officials on Sunday and told them he needed help.