Potential balls indicate a range of possible potentials:
1 ball is 0-2 potential (announcer, bench warmer, role player)
2 ball is 3-4 potential (6th man, starter)
3 ball is 5-6 potential (star, allstar)
4 ball is 7-8 potential (perennial allstar, superstar)
5 ball is 9-11 potential (MVP, hall of famer, all time great)
Potential also has sublevels, with all-time great really being 10.95-10.99, but it's shown as 11 the user manual.