It looks like Alabama has been taking advantage of a NCAA by-law that allows them to invite former players back to suit up for practice. This week in particular they invited former Heisman finalist, and #3 overall pick Trent Richardson back to mimic Leonard Fournette on the scout team. They also invited back 2015 QB Blake Sims to mimic aTm's Trevor Knight.

I can't imagine that this by-law will exist for much longer now:

NCAA bylaw 14.2.1.6, titled “Exception — Former Student Participating in Practice on an Occasional Basis”

“A former student at the certifying institution (e.g., former student-athlete) may participate in an organized practice session on an occasional basis, provided the institution does not publicize the participation of the former student at any time before the practice session.”