Well, without any doubt a superstar player is more likely an asset for a team and thus his presence in the team is what makes fans and team supporters confident about the team or club. Let's say if you like a club only because you know there's a player who always does his best then of course you will get dishearten if that person leave that clubs or get transferred to another club. Not only the fans or supporters but other players of the club also miss such players because without such players it becomes hard to play in the best way possible.