You would be wrong to assume that the best players are the highest lvl, or most stars. Best player in one of my team is 3 stars, and he's League topscorer as well. He degrades my 5* AML to a benchplayer. What's even more funny, .is that I bought him at start of this season from a direct opponent in my league.More often then not the League's top scorers/passers/rated aren't the highest lvl players in the competition. Like Celtic said; player programming trumps most anything. It's your job to identify and spot the weak and the strong in your team and act on it. That's why I prefer young fasttrainers as you can trial and error them and sell them without losses if he fails. That's also why I select my attackers purely on goalscoringstats. And keep in mind, with any new season things can change for your team.
edit in: Even though player ratings can be a bit iffy, avg ratings of 4-6 are a reason for concern, I'ld immediately let him go.