The coach star rating is in comparison to other players at your club as well as their current ability. Because you have RVP & Rooney who are world class players, Chicharito's star rating obviously won't be as high as theirs and is reduced as a result. As for Fellaini, there's no world class central midfielders at United, so his star rating isn't reduced in comparison - and 3.5 stars is what you'd expect to get for a player of that level.
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