Michael Weiner dies at 51; head of Major League Baseball Players Assn.

Michael Weiner, who devoted his adult life to representing Major League Baseball players and rose to become their leader during an era of unprecedented prosperity and labor peace, died Thursday. He was 51.

Weiner, who was found to have inoperable brain cancer 15 months ago, died at his New Jersey home, the union said.

His casual manner and dress belied his stature as one of the smartest men ever to work in sports. His popularity extended beyond the players and their union to the commissioner’s office, and to the very executives against whom he negotiated.

He continued to work through this summer, even as the cancer robbed him of his ability to walk and the use of his right side. Nonetheless, he appeared at the All-Star Game in July, in a wheelchair and in public view. He had no hesitation in explaining why, even as his voice grew soft and the trace of a tear appeared in his left eye.

“I don’t know if I will be able to do this again,” he told The Times. “If the doctors’ prognostications and numbers are right, I probably won’t. Because of that, I want to be wherever I can be.”

In accordance with a succession plan, former major league first baseman Tony Clark becomes acting executive director. The union’s executive board is expected to confirm Clark as Weiner’s successor next month.

Born Dec. 21, 1961, Weiner grew up in New Jersey. His father owned a construction company, and Weiner spent several summers working on union crews.

Weiner graduated from Williams College in 1983 and Harvard Law School in 1986. After two years clerking for a federal judge, Weiner joined the Major League Baseball Players Assn. as counsel, at 26.

He never left the union, working as one of its lawyers during the 1994-95 strike. He rose to general counsel and, in 2009, replaced Donald Fehr as executive director.

Under Weiner — and with revenues leaping to record levels — the union negotiated a new collective bargaining agreement without threat of a work stoppage. The union also worked with the commissioner’s office to tighten baseball’s drug policy.

“He was truly a great individual, a brilliant lawyer and a thoroughly decent person,” Dodgers President Stan Kasten said. “All of baseball — labor and management — has suffered a great loss. Michael was always viewed as the path to a reasonable resolution.”

As news of Weiner’s passing spread, some of baseball’s biggest stars took to Twitter to express condolences to the family of a powerful man who could explain the most complicated and arcane rules in plain English, who disdained fancy suits for polo shirts and sneakers.

From Angels first baseman Albert Pujols, a three-time most valuable player: “Words can’t describe the kind of man he was. I will miss you, my friend.”

From Pittsburgh Pirates outfielder Andrew McCutchen, this year’s National League MVP: “Michael Weiner worked through his sickness. He didn’t look at it an excuse to quit. He never gave up on us even when at his worst.”

At the All-Star Game, Commissioner Bud Selig approached the wheelchair-bound Weiner, lowered his right hand onto Weiner’s left shoulder and exchanged pleasantries. Later, Selig politely declined to discuss his interaction with Weiner, but the anguish was apparent on the commissioner’s face.

“Michael was a courageous human being,” Selig said in a statement, “and the final year of his remarkable life inspired so many in our profession.”

Weiner spoke to the Baseball Writers Assn. of America in July, his voice already wavering, his right side no longer functional, his brain as sharp as ever. He was well aware his days were numbered.

“What I look for each day is beauty, meaning and joy,” he said that day. “If I can find beauty, meaning and joy, that’s a good day.”

Weiner’s survivors include his wife, Diane, and three daughters.

The union said announcements about memorial services would be made at a later date.

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Twitter: @BillShaikin