Revisiting notes by ESPN NFL Insider Field Yates, originally posted in 2012, on how teams scout for players at each position, focusing on safeties:
DESIRED TRAITS: A safety is the ultimate two-phase player; he must be an impact player against both the run and the pass. That means, from a physical standpoint, he must have the core and base to hold up through a high volume of tackles, but also the athleticism to cover in the passing game.
A safety must show reactive athleticism and be able to work laterally and open his hips. He must have the body control to get depth in his backpedal without losing his vision of the quarterback, the fluidity to turn and run, and the speed to keep up with pass-catchers and make sure no one trails behind him. As a pass defender, his ball skills and man-to-man coverage skills must be good enough to hold up against athletic tight ends and bigger wide receivers. In Patrick Chung, the Patriots have an adept coverage man who has enough versatility to both defend seam-stretching tight ends and some slot receivers.
When it comes to defending the run, a safety must show tremendous toughness, grit and tackling ability. A safety will often find himself near the line of scrimmage, meaning he must be reliable to take down runners before they break to the second level. Safeties also make a number of tackles in the open field on the second or third level, further increasing the need for sound tackling form. A safety who is not willing or not able to take on the biggest and fastest running backs is a liability.
Safeties are quarterbacks in the secondary and must be strong leaders and communicators. This involves making his secondary aware of the down and distance on each and every play, having enough savvy to recognize when to adjust to an offensive formation pre-snap, and the smarts to understand the defensive concepts called by his coordinator. When in doubt, his teammates must be able to turn to the safety for answers.
SPECIAL TEAMS ANGLE: A safety is expected to be a core contributor on special teams, with the blend of speed, size and tackling ability to cover and hold up on kicks and punts.
PATRIOTS TAKE: This position has undergone the least amount of change from 2015, with the top four players returning -- starters Devin McCourty and Patrick Chung, followed by Duron Harmon and 2015 second-round pick Jordan Richards. Special teamer Nate Ebner, who has spent this offseason vying to become a member of the U.S. rugby team, also returns, with 2016 sixth-round draft choice Kamu Grugier-Hill also in the mix as a linebacker/safety type hybrid who at one point in spring practices was lined up as a gunner opposite of captain Matthew Slater. In terms of playing style, McCourty and Harmon are linked as more center-field types, while Chung and Richards have some similarities as safeties who might be asked to play in the box more often. The lone departure from last year is Tavon Wilson, who signed with the Lions as a free agent. Overall, the Patriots appear to be in good shape at this spot.