Robert Calvin Hubbard (October 31, 1900 – October 17, 1977) was a professional American football player and Major League Baseball (MLB) umpire. After playing football at Centenary College and Geneva College, Hubbard played in the National Football League (NFL) between 1927 and 1936 for the New York Giants, Green Bay Packers and Pittsburgh Pirates, playing the bulk of his career with the Packers. Hubbard is credited as being one of the inventors of the football position of linebacker.He was also an umpire in the American League (AL) from 1936 to 1951, then worked as an umpire supervisor until 1969. George Halas affectionately called Hubbard the "Big Umpire."To date, Hubbard is the only person to be enshrined in both the Pro Football Hall of Fame and the Baseball Hall of Fame. He is also a member of the College Football Hall of Fame.