I know there's a general thought that Jalen doesn't have the lateral quickness to play RB, and on the surface that would be the case and I would agree.And the question then becomes "If Tua unseats Jalen next spring/fall what does Jalen do?"
Then there is the case of Derrick Henry, who was not quick at all laterally. He DOMINATED a year of college football and if he was getting more carries would probably dominate the in the NFL also.
it's also likely Jalen's never really focused on lateral agility and quickness due to his position. With a little work he might improve it greatly. He has the strength and agility so it could just be a matter of reps.