It was September, the game didn't mean much, and the Yankees used their bench accordingly.
By September 29, 1956, the Yankees had already clinched the AL pennant. Going into that day's game, they were nine games up on the second place Indians with just two games to go. In the National League, the Milwaukee Braves led by half a game over the Dodgers, with the Reds just two games back. So, when the Yankees took on the Red Sox on September 29, they didn't really have much to play for.