The MLB Players Association executive director Michael Weiner passed away on Thursday and the news was a shock and surprise to many in the sports world, even though he was previously diagnosed with a brain tumor and now Tony Clark will serve as the leader of the union now that Weiner has passed away.

Weiner replaced Donald Fehr as the leader of the union about five years ago and he was part of the group the helped bring on changes to instant replay as well as the playoff format and his death comes after he announced last year that he was dealing with a brain tumor. Major League Baseball Players Association executive director Michael Weiner died on Thursday after a 15-month battle with brain cancer. Weiner was diagnosed with an inoperable brain tumor in August 2012 but continued to serve in the role he took on in late 2009 when he replaced Don Fehr.

The 51-year-old was credited with major benefits accruing to players from the 2011 collective bargaining negotiations, his first while in charge of the union. He had served in the union's counsel's office since 1988. He was also involved in the addition of a second wild card team in each league, the creation of two 15-team leagues, approval of expanded instant replay and the institution of new protocols and procedures with regard to concussions.

"First, I want to extend our sincerest, heartfelt condolences to Michael's wife, Diane, and daughters," MLBPA deputy executive director Tony Clark said in a statement.

"Words cannot describe the love and affection that the players have for Michael, nor can they describe the level of sadness we feel today.

"Not only has the game lost one of its most important and influential leaders in this generation, all involved in the game have lost a true friend."

(Reuters)