Ok well first lets explain the type of player Kenny Vaccaro is, he is a very athletic/smart safety. He is a combo safety but his best fit in the NFL is at Strong Safety. Why? Because his best attributes are man coverage and change of direction skills, ur free safety is almost never in man coverage unless its an all out blitz. He had one of the best 20 yard shuttles in the combine, which is a drill to determine a players change of direction ability. I dont like him at Free Safety because he is very aggressive and tends to leave his zone and go for the big play, not what u want at FS. He also has good size at 6"1 218. An awesome 38" vertical and can lay the wood. Also has great body movement and control.
So why he fits the Saints scheme. Roman Harper was so good with Greg Williams because he was allowed to do what he does best, be in the box and blitz. With Rob Ryan the defense is totally different, he doesn't call for his SS to blitz, but to play man up coverage on tight ends or slot WR's.
Why does Rob Ryan do this? Because of his scheme: - Cover 1 Press
Rob Ryan runs a Cover 1 Press about 75% of the time. What is this exactly? Its simple. In this scheme all of ur corner backs will be in man coverage and press(jam) their wide receivers at the line of scrimmage. The Cover 1 means there is only ONE safety playing in a deep zone, everyone else is manned up or blitzing. In this scheme with the 3-4 defense u are sending an extra blitzer in place of your second guy who would be covering the other deep zone. Therefor Rob Ryan will blitz all 3 defensive lineman, and BOTH OLB's. You need good press corners to do this and a VERY good SS at man coverage with a good vertical to compete with tight ends.
Roman Harper is the worst possible fit for a Rob Ryan defense, he isnt a bad player, but in this scheme, u need a lockdown man coverage SS. Great Pick by us!
-One other thing, Vaccaro is supposed to be excellent at stopping the Quarterback option because of his instincts, read and react skills, and change of direction agility skills. We will need this vs cam newton, colin kap and russel wilson.