A player who is considered an eligible receiver can keep his original number after a position switch, as long as he remains at an eligible position. For example, Devin Hester was allowed to keep #23 after converting from running back to wide receiver, even though #23 is not within the range of numbers allowed for wideouts entering the league. Same logic is at work for Robinson: he was a wideout last year and wore #16, and even though he's now a running back, he's allowed to keep that 16 because he's switching from one eligible position to another. If a player were to switch from, say, TE to OT, they would be forced to switch numbers, as their new position is not receiver-eligible.

 

Devin Hester switched to #17 in Atlanta because #23 was taken. Dri Archer is allowed to wear #13 because he's listed as a "WR/RB" by the Steelers.

---