van Zegeren's skills are more suited for a 4 than a 5. Barksdale most likely Raines backup at this point.
Really, it depends on how much muscle mass JVZ is able to put on before the start of next season. If he and Barksdale are around the same weight, you'll see JVZ guarding the center because of his height. Centers with good offensive post moves will abuse Barksdale. Also of note, it may be different under JJ than it was under Greenberg, but in the few games where JVZ was on the floor at the same time as Barksdale, JVZ was at the 5 and Barksdale was at the 4.