How to know the "absolute value" of a player?

[Rizla]

For example, stars => if I understand well, players stars depend on the leagues your team is playing in? (and when you're promoted, some of your players may lose a star, because they're not as good as they were in the previous league... right?)

All the players lose a star if the team promote to next level.
Player 1 have 50% speed for managers at level 2
70% for manager at level 1 and 30% for managers at lvl3 etc
So the manager who is at level 50 he will see the player one with speed ability 1%
(it's much lower but the system shows only >1%.)
There are a bunch of newbies quides on this forum you may consider
to take a look at them.