of this list, I'd say Hayward and Hyde for the first half of his first season away from Green Bay stand out. That's a short list.
Those guys have been playing consistently good football since they left.
I don't think LAC gave Hayward a 3 year/$34.25 mil/$20 mil guaranteed deal for nothing going into 2018. Perhaps the best statistical measure of a DB's coverage ability is how often opponents throw in his direction. Who do they fear? Hayward drew only 56 targets last season, 69th. in the league, at a good 57% completion rate.
https://www.pff.com/nfl/players/casey-hayward/7064
That was on a 98% snap count with opponents throwing the ball against LAC 548 times, a little above the league median average.
In 2016 - 2018, Hayward's INT + passes defended were 27, 26 and then 8, in that order. Big fall off, right? There were only 24 balls thrown against Hayward that were not completed last season despite Hayward's good completion rate. It would been impossible to match the earlier numbers on those not completed passes.
When discussing these kinds of stats I'm always reminded of Nnamdi Asomugha. During his three Pro Bowl/All Pro seasons in Oakland, his INT + passes defended were 9, 4 and 6, including only two INTs over those three years. Overrated? Not when you consider opponents were throwing at him at a ridiculously low 20-some times per season.
Using a familiar comparison, teams threw at Alexender 79 times for a 65% completion rate last season while having several other guys being more challenge-worthy.
https://www.pff.com/nfl/players/jaire-alexander/49350
That's on a 71% snap count, with one INT and 11 PDs, with opponents throwing the ball 527 times, 10th. fewest in the league.
[Note: There is a general correlation between winning and more throws against. That stands to reason. Trailing teams throw more and leading teams run more later in games.]
I think we all agree Alexander had a darn good season for a rookie. If he progresses as we hope, those targets/snap will go down and his INT + PD per snap will go down right along with it. Teams will look elsewhere.
Safety play is probably the hardest position to evaluate since most of what they do is off the screen unless you're going to scour the player's all-22 video at NFL Game Pass. PFF put Hyde in their top 100 players for 2018, which is probably as good an assessment as you're going to get without watching all those all-22 plays yourself.
Buffalo led the league in fewest passing yards per game surrendered (179 yds.), though that's a little deceptive since they had the second fewest balls thrown against them last season. Again, losing teams get thrown against less. However, their 82.6 passer rating against ranked 3rd. in the league. You might reckon Hyde contributed to that.
It's easy to say in hindsight that letting these guys go was a mistake. It is also easy to say Hyde was a mediocre slot corner which is where he played when Burnett wasn't injured. I don't think it was easy at the time to say keep him to play safety and get rid of C-D or Burnett. Hayward was also not exactly burning up the track after his rookie pick fest.