Cal Hubbard Robert Calvin Hubbard ( October 31 , 1900 – October 17 , 1977 ) was a professional American football player and later an umpire in Major League Baseball . A member of three major sports halls of fame , Hubbard is credited as being one of the inventors of the football position of linebacker . 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 . Early life . Cal Hubbard was born in Keytesville , Missouri to parents Robert P . and Sarah " Sallie " ( Ford ) Hubbard . He grew up in modest means as the son of a small family farmer . Cal graduated from Keytesville High School , but because the school had no football team he also attended one year at Glasgow High School in nearby Glasgow , Missouri , which did offer football . Already tall and weighing 200 pounds as a 14 - year old , Hubbard displayed natural athletic gifts . He aspired to attend the United States Military Academy at West Point , New York however a physical discovered he had flat feet , eliminating him from eligibility . Instead Hubbard chose to attend a college or university that offered football , selecting Chillicothe Business College in Chillicothe , Missouri while also continuing to work around his family farm . A chance meeting in 1922 with Bo McMillin , the new football coach at Centenary College in Shreveport , Louisiana , led Hubbard to enroll and play football there from 1922 to 1924 . When McMillin moved on to suburban Pittsburgh ' s Geneva College , Hubbard followed him and played there in 1926 ( after a year of ineligibility for switching schools in 1925 ) . Noted for remarkable speed for a player of his size ( 6 ' 4 " , 250 lb or 1 . 93 m , 115 kg ) , he starred as a tackle and end , playing off the line in a style similar to that of a modern linebacker . Hubbard completed his college education in 1927 , earning a Bachhelor of Arts degree from Geneva College . Professional career . Football career . Hubbard moved on to the National Football League in 1927 , signing with the New York Giants for a salary of $ 150 per game . Playing alongside Steve Owen his rookie year , he helped the Giants defense allow opponents to score just twenty total points all season as they won the league championship . For his efforts Hubbard won all - league honors by the press the following year . But with a lifelong dislike for big cities , he didn ' t feel comfortable in New York and a 1928 road game in Green Bay led him to request a trade to the Packers , threatening to retire otherwise . Under Packers coach Curly Lambeau , Hubbard and the team won the NFL title in each of his first three years there ( 1929 – 1931 ) . The NFL named its first official All - League team in 1931 with Cal Hubbard being one of that inaugural list . He was chosen for the honor again in 1932 and 1933 . Hubbard stepped away from professional football following the 1933 season , taking a job as the line coach at Texas A & M in 1934 . However he was persuaded to return to play after that one year on the sidelines , returning to Green Bay in 1935 . The Giants wooed him back to start 1936 with them , but he played only six games the entire season , five for the Giants and a final game for the Pittsburgh Pirates , the future Steelers . Cal Hubbard returned to football coaching briefly , serving as head coach of his alma mater Geneva College in 1941 and 1942 . He was among the initial class of inductees to the Pro Football Hall of Fame in 1963 . In a 1969 poll by the Hall of Fame commttee , Hubbard was voted the NFL ' s greatest tackle all - time . Baseball career . Even while Hubbard ' s football career was going full - force he began to focus on a second career in baseball officiating . From 1928 onward he spent his football off - season umpiring in minor league baseball . By 1936 Hubbard had been called up to the major leagues , umpiring in the American League from 1936 to 1951 . Soon recognized as one of the game ' s best officials , he was selected to work in the 1938 World Series , followed by Series appearances in 1942 , 1946 & 1949 . In addition , he umpired in the All - Star Game in 1939 , 1944 & 1949 , behind the plate for half of the 1939 & 1944 midsummer classics . As an umpire Hubbard found the then - common practice of officials moving to different positions on the field during a game to be confusing and hampered accuracy when making calls . Applying his football experience to baseball , he devised a system where each official had clearly defined duties and also added an additional official to the crew . This was the foundation on which Major League Baseball established new officiating standards in 1952 . While hunting during the 1951 off - season a ricocheting pellet from a friends shotgun blast accidentally struck Hubbard in the right eye . The damage was extensive enough to force his retirement from baseball officiating . However the American League soon hired him as an assistant supervisor for league officiating crews , and in 1954 he became the top supervisor , a position he would hold until retiring for good in 1969 . In recognition of his contributions to the game as an umpire and supervisor , Cal Hubbard was elected to the Baseball Hall of Fame in , only the fifth umpire to be so honored up to that time . Final years . Never a fan of big cities , Cal Hubbard first settled in Milan , Missouri in 1944 . He left in 1945 but moved back in 1948 for good . Milan was a small town much like his native Keytesville , which is about fifty miles to the south on Missouri Route 5 . A lifelong avid fisherman and hunter , the rural areas of Sullivan and neighboring counties offered ample opportunity . Hubbard stayed involved in community affairs , especially children ' s sports , as much as his schedule would allow . In honor of his efforts the football field at Milan High School is named Cal Hubbard Field . Cal Hubbard died due to cancer October 17 , 1977 at age 76 in St . Petersburg , Florida . He is buried in the Oakwood Cemetery , Milan , Missouri . He was survived by wife Mildred and two sons , Dr . Robert Hubbard , and William " Bill " Hubbard .