Zimmer was involved in a brawl with Pedro Martínez in the 2003 American League Championship Series, when he ran at Martinez and Martinez threw him to the ground. Zimmer accepted responsibility for the altercation and was apologetic to his family and the Yankees organization but maintained that Martínez was "one of the most unprofessional players" he had ever known. He was also once hit by a sharply struck foul ball batted by Yankee second baseman Chuck Knoblauch. The next game, Zimmer wore an army helmet with the word "ZIM" painted on the side and the Yankees logo stenciled on the front, which was given to him by Michael Patti, a Madison Avenue advertising executive. That event led to the installation of railed fencing in front of the dugouts at Yankee Stadium, which eventually became commonplace at all ballparks.