Why is Coleman even that much of a concern ? The safety position is the least stategic position, least difficult position on the D side of the field to fill. Coleman is clearly an outstanding athelete, but he lacks the all important attribute of superior natural speed to be a pure corner - thats what D.Robinson has in spades and for more than any other reason, that is why we used our 10 overall on him.
You can always staff the safety position with over-the-hill, burnt-out
corners who no longer can keep up with the speed guys at WR(or were never true corners in the first place because of lack of superior speed), or pick them up in the 3rd, 4th, or > roound in the college draft. Coleman is a fine athelete and good football player who is too slow to be an above average corner and too small to be a LB.