There is the possibility that it is not confidence but cognitive.
In my job I have worked with many talented people and some of them just struggle to follow a clear set of instructions. They can still create fabulous designs, but in an unconventional manner.
I doubt the mercurial talents of Best and Gascgoine would be as welcomed in today's world of peak athletic discipline.
Ross has a gift as a footballer. Finding the right way to bring that talent out correctly has proved a challenge for all of his managers though.
The trouble with Barkley is, he is one of those people with an immense, natural talent, but he only applies it sporadically, when the stars are aligned in his mind, or when the mood is right or inspiration strikes. The giant quote in the Everton gym, "Hard Work Beats Talent When Talent Doesn't Work As Hard", seems lost on him at times, and that is what frustrates me the most. I could be wrong, and way out of order, but the lad seems to be missing a few cognitive cogs at times. Sorry, Ross, but that's the impression I get.