I like the idea of Green's physical style of play at CB...But, if we are talking about converting a Safety to CB, I would rather draft Boston College Safety Justin Simmons. Simmons is 6-2 202 lbs. with 32 5/8 inch arm length, he has better ball skills than Green and Coach Carrol wants his CB's that can play the ball. Simmons last two years he had 7 interceptions with 7 PBU's and Green had 1 interception with 3 PBU's. If we had to take a safety and covert him to CB, then I'd prefer Simmons.
Green's combine/Pro Day numbers,
40-yard: 4.34
10-yard split: 1.52
vertical: 35 1/2
broad jump: 10'9"
3-cone: 7.10
20-yard shuttle: 4.41
bench: 13 reps
Simmons's combine/Pro Day numbers:
40-yard: 4.53
10-yard split: 1.56
vertical: 40
broad jump: 10'6"
3-cone: 6.58
20-yard shuttle: 3.85
bench: 16 reps
Both Green and Simmons have similar size, but Simmons has the better ball skill, along with the better #'s in CB transferable tests. Give me a CB that has good agility (3-cone/20-yard shuttle), along with a good 10-yard split & vertical jump. For me 40-yard times are overrated for CB's, especially if that fast CB doesn't have the ball skills to make a play on the ball.
If we were taking about converting a Safety to a hybrid LB/S, like the Cardinal's Deone Bucannon, then I would choose Green over Simmons.