I'm sure Chris Johnson Jr has a lot of aspects he can still improve upon, and he needs to work hard at them. And maybe he hasn't been the most impressive over spring. But that is pretty meaningless to me. What we need from Chris Johnson is not some great consistency at 6ypc EVERY carry or some grinder, which is kinda what spring ball is about. We need a guy who when he comes in is a threat in the receiving game, can pick up in the 4-5 ypc range in general, but most importantly has like 2-4 15+ yard runs in him per game. I was never a fan of Camron Harris because imo he was too hit and miss - either 60 yard run or 2 yard run. CJjr has that 60 yard run capability, but all he needs is to try not to get too cute dancing behind the line and just be a guy that you can trust will hit the gap as fast as he can and pick up 4 yards - and if our great Oline blocked well he'll be at 10-15 yards in the blink of an eye. Great OL + elite passing attack is going to be CJjrs best friend. Plus we can use Martinez (and next year Fletcher) to grind teams down too.
Ultimately he has an elite trait - speed. I'm not someone who thinks world-class sprinting speed ALONE is the most important thing at RB - especially if its long speed and not paired with great acceleration/burst. In general I don't think being the absolute fastest generally makes for the BEST RBs. BUT it can make for extremely useful RBs especially as a pairing to a guy like Martinez and Fletcher. Having said that, there is a pretty strong relation imo to speed score and success (so weight adjusted speed) at RB. This means you can't be a 170lb Blazer at RB, you won't have the necessary strength to run through gaps. That's why these types end up at WR. But if He can get to a playing weight of 190lbs or ideally 195lbs, I really think most of his problems will just work themselves out or the downside will be well worth him seeing a lot of reps anyways. Right now he's listed at 180lbs, which is fine - and probably the minimum he needs to be at. But add another 10lbs and his elite speed and good enough strength will make him a productive asset.
Also there isn't a position I'd be more confident about a guy just being a gamer than RB. A dude with just pure talent can just be good, regardless what the negatives appear in practice. At the end of the day do you want this guy with the ball in his hands or not?