Hi,
When you see your players, you see the external skills, attributes, stars, etc
Bt every player have hidden skills, limits of contribution (the game regulates this, to dont have 11 or 11 super players, so yo can go to the market, and buy 11 players that scored 30 goals each the last season, but, once you buy them the game calibrates your team to have some "best" players, and some worst, some that will contribute more, and some less, 1 player usually will be the choosen to score in more % from Freekicks for example, another will, during a "considerable space of time" be the best in Corners with differance, this will be stable because the game is not so paranoid to change the contribution that players do every day, the game want you manage and see what players are the best, the game want you tesing them.
You can have for example 2 exact ST's, same age, tall etc but one, for example will score 40 goals with 5 stars, and the second, with 9 stars will score 3 in all the season. Thats why theres a internal min./max. of contribution or "ratio score" that can be achieved for every player.
Thats the internal programmng I mean.
Too, there are MC's that help a lot in defense, players that, you see their name often every match and players that appear one match yes and one do not....
All this belongs to the internal programming and if you understand it, this will help a lot.
When I say "bad programmed player" I mean this, you can have a 9* ST programmed to score as a Max. 1 of 10 chances and that is programmed to do not appear often so is ot a key player despite his 9*. A well programmed player, ST-AMC-or so, with 5* reach almost the max. of contribution that can give, having abig ratio of appearances almost evey match, scoring often, having some MoM....
Well, more or less I explained xD