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AlbaNY_Ram
Joyner played more of a strong safety in 2017 and acquitted himself well in that role. PFF had him as the 3rd best safety in the NFL and 52nd best player overall after that season. [www.turfshowtimes.com] "His overall PFF grade of 90.3 was the third-best mark among safeties, but also more than 10 grading points better than his previous NFL high of the season before." (Note: statistically, Joyner had his best season under Wade, not Williams ...)

Then JJ emerged as an even better strong safety so Joyner's role evolved into more of a free safety position in 2018 ... and it turned out that Joyner isn't particularly suited to that role. Joyner's PFF grade dropped from 90.3 to 73.1, and he dropped from the #3 safety in the league to 28th. [theramswire.usatoday.com]

I suspect that Joyner will once again have a fine season with the Raiders, but since he wasn't going to beat out NRC at slot corner, wasn't going to beat out JJ at strong safety, was prohibitively expensive as a backup, and netted the Rams a 4th round comp pick due to his contract (4 yr., $42M) it was simply time for he and the Rams to part ways.