When I watch Jack, the problems I see with him are mostly about the mental aspects of the game. Those can be taught and learned through experience. He's got physical abilities that no one can teach.
I have no problem with selling Jack as long as it's a fair price. Considering his potential and intangibles, I think that price is 25 mill right now. It's a risk to keep him as there's always a chance he never makes it and starts losing value. But do we really want to play it safe? We've been playing it safe for years and are still knocking on the door of the "elite 6's" party.
I disagree, his physical attributes are naturally acquired. His height, pace, stamina, strength, they are great attributes to have but its discipline, drive, vision, timing, these are the traits he's missing, that he needs to acquire to be a success at this level, and they are by no means a formality.
And even so we're hardly knocking on their door. Its taken Spurs winning one since February, and our best run of the campaign to get anywhere close, and even now we need a minor miracle to finish above them on goal difference. We're the best of the rest, though I think it will take a bold move, such as selling Baines, Fellaini and Rodwell to restructure this team so we are able to knock on the door of the elite 6 (i've never heard them called that before !)
And bear in mind the likes of Villa, Newcastle, Bolton, Sunderland and perhaps one or two others will be spending big this summer to push on, so its not just a case of looking up, we'll do well to maintain that position next season if we don't see some investment.