Ok, assuming that Laron Landry (who is by far the best fit for our D as he is big, fast, strong, versatile, and intelligent), is out of our draft position barring a trade up, there's three safeties we should be looking at, Reggie Nelson, Michael Griffin, and Brandon Meriweather.
First let me say that the NFL is shifting less towards traditional safeties, and more towards hybrid safeties that can do everything. Think Ed Reed, Bob Sanders, etc.
A look at our safeties makes one thing evident, our strong safeties are significantly bigger than our free safeties
SS
Rodney Harrison, 6-1, 220 lbs.
James Sanders, 5-10, 210 lbs.
FS
Rashad Baker, 5-10, 198 lbs.
Eugene Wilson, 5-10, 195
Artell Hawkins, 5-10, 195
There's two things that you expect your strong safety to be able to do, go in the box to stop the run, and cover tight ends. Let's take a look at the three safeties that the Pats have to choose from
Michael Griffin (6-0, 195), out of the three Griffin has the best size, BUT he is much better suited for free safety at the next level, he's bad against the run, and will get man handled by blockers, that being said his ability to cover is second to none, he is a better prospect than Michael Huff was last year, hes also a great st'er, and will make some plays there for us
Reggie Nelson (6-0, 193), Nelson has a similar build to Griffin, and is my choice for the Pats, he's intinctive, and field smart, and plays faster than he times, he's a hart hitter and won't be afraid to support the run, but can also cover, he's very versatile, might might need to add a few pounds to keep up with some of the tight end's that are around, but he would most definently help the Pats the most with Griffin being a close second
Brandon Meriweather (5-11, 192), Meriweather is basically Nelson with better speed, but character concerns, and durability concerns are more prominent than with Nelson