PRob was drafted primarily cuz of the man cover skills he had. Switching to the zone coverage prolly impacted him more negatively than any other player. This is shown in this PFF study of CBs.
He and two other CBs were the first in history to allow over 1000yds in coverage. Out of 619 coverage snaps he played in this comes out to 1.73 yards per snap. That ranks 111th out of 115 cornerbacks. Note that Tracy Porter was even worse.
In info that has leaked out it becomes clearer that a great part of Spags failure was trying to fit square pegs into round holes.
Robinson flashes some obvious skills. Making better use of what he does best could be a vital component of major defensive improvement. Certainly such things will be key in decided on the next DC.