NFL Connections #70, Answers
The full solution: all four groups and the 16 names, sorted from the easiest group to the trickiest.
Cowboys workhorse backs
Emmitt Smith, Tony Dorsett, DeMarco Murray, Ezekiel Elliott
Bills running backs
Thurman Thomas, O.J. Simpson, Fred Jackson, LeSean McCoy
Steelers running backs
Franco Harris, Jerome Bettis, Le'Veon Bell, Najee Harris
Broncos running backs
Terrell Davis, Floyd Little, Clinton Portis, Mike Anderson