No he won’t!
Kid has never had to line up behind the defensive line and read and react. Just rushed the passer from the line of scrimmage.
No way he will ever make a good MLB here.
Keep him on the outside where he won’t get overwhelmed and where his lack of LB instincts don’t hold him back as much.
Joyner is more in the mold of a OLB/WDE hybrid or Viper in 3-4 defenses.
That position can still be used out of the 4-3, but it is more rare, and kind of shows your hand that he will be blitzing unless he learns to play in space.
Thank you. Acting like it's easy for a DE to "convert" to MLB betrays a profound lack of football knowledge. You don't just learn to read and react overnight.