How does it alter players stats exactly? What I really need to know is does it change their stats that normally don't change or only the ones that show where they are now and where they can potentially get to?

Also does it ever make the potentials go up, or only ever down?

Thanks

Only football skills change, physical attributes only change with age.

Volatility indicates how much the blue will move until the red catches up with it. It does not indicate which direction it may move, so yes, it may go up or it may go down. Low volatility will not move much.

So high volatility just means that the 'max' values are probably going to move until the 'current' value catches it.

I know this is an old topic but, if there is a high volatility on a player with a high potential, is it all but guaranteed to go down?

50% chance it will go down. If his future is already peaked it won't go up, but it's a higher risk because there is that 50% chance it will go down with 50% chance it will only stay the same. So the risk/reward is indeed heavier on the risk side than someone who is a lower future value and has the 50% chance that he will boom, but there is not more than a 50% chance that he will decline.