If you are not concerned, then you are ignoring a lot of signs. The only sign that he'll be a good player, is his production in college. He is slow, as evidenced by producing the slowest 40 time in memory for a 1st round LB. So (1), he is slow. He is also, by his own admission, not strong enough (2). And the last thing of course being, he was a non-factor, actually playing in the league in question (the NFL). Remember also, he was supposed to be plug-and-play ready. Even if he ended up not being so, you would certainly expect him to have flashes of success (i.e. a few sacks?)
I'm not writing him off yet, but I am concerned. How can you not be?
Strength is a non-issue.... That is the easiest to fix. Timmons was the same way.
1. If a LB has to run 40 yards for any reason, something went totally wrong anyways.
2. Like Steelz said, strength can easily be fixed.
3. Plug n play ready in a very complex system like LeBeau's is never going to happen.
I sincerely believe he can produce at this level by hitting the gym and studying the playbook. He's a natural athlete and you can easily see that by watching him play.
If that is the case, why aren't we drafting Aaron Donald, putting him in the weight room, and let him plug the middle (on 1st & 2nd) and rush the passer (on 3rd)? You know the reason why... because it isn't as "easy" as getting a guy on a bench press. Many people get stronger, and lose speed. For Jones, that would be a disaster.
I don't see how JJ gaining strength will make him slower. In fact, I think he could add a bit more bulk as well without losing speed. He has the frame to easily carry 10 more pounds of lean muscle. He's taller than most think: 6'2.
Troy Polamalu was a non-factor in his rookie season.
Pittsburgh, PA: City of Champions.