So I've asked this questions here and got only vague answers. Someone believes it doesn't matter at all, someone thinks otherwise.
yes, there are many things that cannot be answered (only by the developers/programers of game - but don't expect such thing), so everyone has a point of view by his experience from the game.
I rather agree with Khris, that maybe there few factors that affect the game but this is only a percent of 1-2-3% (?) so it's not easy observe this. Specially if consider the formation & orders which has a big effect in the process of the game as also a roll dice.
My recently experience from this season was that after the star of team, my ST, Neymar, lost his form in the beginning of the season, I set as captain my 2nd best player, my AML Eder. The team is keeping winning, EDER didn't lost his form and Neymar got his form back.

I don't know if it happened when I benched him for few games or when I bought another (good performer) ST Zardel and they did a perfect duo.
Well, that's the game

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