On October 6 , 2010 , in his first career MLB playoff game , he threw a no hitter against the Cincinnati Reds , allowing only one walk . On October 6 , 2010 , in his first post-season start , Halladay threw the second no-hitter in MLB postseason history ( Don Larsen 's perfect game in the 1956 World Series being the first ) against the Cincinnati Reds in Game 1 of the 2010 NLDS .