What position did Gale Sayers primarily play?

What jersey number did Tony Dorsett wear with the Cowboys? What position did Earl Campbell primarily play? Which college was Earl Campbell playing for when he entered the NFL? What jersey number did Earl Campbell wear with the Oilers? Gale Sayers is best known for playing with which NFL team? Which college was Gale Sayers playing for when he entered the NFL? What jersey number did Gale Sayers wear with the Bears? What position did Marcus Allen primarily play?