My own (deeply unique and highly original) “theory”© on what happened to Joyner in 2018 is that he was simply not suited for the deep middle role and was better as a nickel safety mixing it up underneath. It’s not a physical thing, I don’t think he had the “in the head” talents for the deep middle. He wasn’t as instinctive in that role.
The BEST thing is if either Countess or Christian can come through as a FS.
But they have a long good record of drafting DBs too.