Viking secondary for a LONG time has been completely bare of talent. Last year Smith and Rhodes look like they can play in Zimmer's system just fine....but they needed more bodies back there.
Instead of drafting it and forcing it to play early, Zimmer has obviously decided to bring in players he knows can make his system work in the short term.
They just signed Taylor Mays from Cinci as well (Zimmer was defensive coordinator of Cinci from 09-13 before being hired as the Vikes head coach).
One of the interesting things about this is that Newman's agent is the same agent for Adrian Peterson (who reportedly refused to meet with the Vikes this week). So there must be some back and forth going on between the two sides.