A relative comparison to Riewoldt in terms of development is probably apt as both are around similar size (although different positions on the field it is the development curve that is of interest).
Riewoldt played against men in the VFL when 17, whereas Post has an extra season at TAC level as a 19 year old which promoted his draft prospects, but probably limited his immediate AFL impact.
There are a couple of AFL pre-seasons involved in this delay, and that is where Post is probably at compared to Jack, 2 years behind relative to debut.
Would want to see Post get an extended run in the 1's for 10+ games (if form warrants) in position as a 2nd defender and determine if he has the potential at B level or higher in 2013.