Major League Baseball Players Association Executive Director Michael Weiner began treatment for a brain tumor on Monday, the MLBPA announced.

Weiner will undergo treatments for about a month, but is still expected to work out of the Union's office in New York regularly during this time.

"On behalf of Major League Baseball and the 30 Major League Clubs, I send my best wishes to Michael Weiner and his family," MLB commissioner Bud Selig said. "I have great respect and admiration for Michael, with whom we have had a very constructive relationship both professionally and personally. This relationship has been a great benefit to Baseball and has led to the tremendous success the game now enjoys. All of us look forward to Michael's full recovery and to his continued contributions to our game."