[tessl]

There is no definitive answer but it seems the better numbers they have combined with potential determines whether their attributes increase or decline.

I don't use A because I consider that cheating since players at that level never get injured due to the fact they don't play games.

I tend to leave my best prospects at AA where they can produce good numbers.
Regarding the actual potential rating it can increase but does so infrequently.

Some things about progress - speed never increases. It only remains the same or decreases at a rate of -1 per year. Pitcher stamina rarely increase and if it does increase it's +1 per season. Sometimes it is unchanged. Most of the time it declines -1 per season. When scouting prospects for the draft ignore the potential screen that shows speed and/or pitcher stamina increasing. I cracked the code to determine exact ratings for fully scouted prospects and posted it on this forum. If interested I can post it in this thread.