no the potential works every training on a new basis, and not on the basis of beginning of the new season ...
The function is kind of the calculation for the salary, and for that the skill level is improtant ;)
Yes, potential checks a "salary-like" variable at each training. And yes, skills are important, but so is the suggested position, so when you say "someone's skills are 10-11", this is only half-informative as far as potential is concerned.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."