Dave Boswell, Major League...

...pitcher, died at age 67. Boswell won 20 games for the Minnesota Twins in 1969, but was also known for getting into a fight with his manager, Billy Martin (my emphasis): 

Accounts differed. Martin said he had confronted Boswell at the bar after the Twins’ pitching coach, Art Fowler, reported to him that Boswell had refused to run his customary laps before the game that evening. 

Boswell then got into a fight outside the bar with Bob Allison, a Twins outfielder, who, as Martin told it, was trying to calm him. Martin said that when he got outside, Boswell hit him as well, at which point Martin’s peacemaking efforts collapsed, as did Boswell. 

Martin retaliated by landing “about five or six punches to the stomach, a couple to the head, and when he came off the wall, I hit him again,” he told The Associated Press, adding, “He was out before he hit the ground.” 

Boswell told The Minneapolis Tribune that he had indeed hit Allison, but denied going after Martin. He complained that Martin “really mauled me.” He received numerous stitches in his face, and Martin had his right hand stitched up. Boswell was fined for the incident, but no action was taken against Martin. 
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Martin was fired by the Twins soon after their 1969 season. 
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The Twins released Boswell in the spring of 1971, and he was picked up by the Tigers. He went on to pitch briefly for their new manager, Billy Martin.