No, "game does not depend on external attributes"- to be more precise aas at some point train grow the Avq, what affect the chances, but regarding the individuality of a single player, /performance it is different IMO.
1- Probably if the 2*is trained till 6* will perform better and with differance than the 6* that actually faced.
2-The 11 main players are increasing the Main Avq, and the distance between the main Avq's of 2 teams are what set the scenario.
3- as said, the external attributes affect very slightly to the players performance, as every single player have internal skills and parameters set by default.
A non contributive player -one that dont show the name in the written live simulation- cant be suddenly, a "Key player" scoring a goal per match.
Is a matter of weights, and internal weights really. Think that 2 exact players, as a easy example to explain, 2 STs can have same stars, profile, etc, but one can be programmed to score the 35% Max. of attempts and the 2nd a Max of 3%. , then if you keep the 1st in 5* (EX.) and you grow the 2nd till 9* this Max. Cap will remain.