It was Todd Haley in 2012 when he took over as offensive coordinator of the Pittsburgh Steelers who really began to make serious use of the sixth offensive lineman as a tackle-eligible receiver. It was a way to get another big body on the field for blocking purposes, of course, but it’s also served as an apprenticeship for young linemen to get valuable in-game experience.
In that first year, it was Mike Adams in that role, then Kelvin Beachum until he took over a starting job. More recently, Chris Hubbard served in that role for a couple of years, and then Chukwuma Okorafor did it as a rookie in 2018.