Conversation so far:
Who does Carlton Fisk have a feud with?
Carlton Fisk was known for his longstanding feud with New York Yankees catcher Thurman Munson.
What caused the feud between Carlton Fisk and Thurman Munson?
Munson, attempting to score on Gene Michael's missed bunt attempt, barreled into Carlton Fisk, triggering a 10-minute bench-clearing brawl in which both catchers were ejected.
What occurred during the feud between Carlton Fisk and Thurman Munson?
Carlton Fisk kicked Munson off him and into the air, and swiped at him with his fist. Fisk threw Michael down with his left arm and fell to the ground.
Who were the catchers that were fighting in Carlton's Fisk feud?
The catchers were Carlton Fisk and Thurman Munson.
Were there ever any injuries between Carlton Fisk and Thurman Munson?
Carlton Fisk had his arm across Stick's throat and wouldn't let up. Michael couldn't breathe. I had to pry Fisk's arm off Michael's throat to keep Fisk from killing Stick.“
Was there any more violence between Carlton Fisk and other players?
Piniella barreled into Carlton Fisk trying to score on an Otto Vélez single. Fisk and Piniella shoved each other at home plate, triggering another bench-clearing brawl.

Question: What was the cause?
Self-contained rewrite: What was the cause of the fight between Carlton Fisk and Lou Piniella?