Maybe he just needs a fresh approach to things. A new face to come in and shake things up for him. Going by that article, he didn't do too badly last time he didn't have a coach!
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Of all tyrannies a tyranny exercised for the good of its victim may be the most oppressive.... those who torment us for our own good will torment us without end for they do so with the approval of their own conscience
Fed has been in pretty poor form recently so a new coach might rejuvenate him a bit. It does seem a bit of a knee-jerk reaction, but I guess no one really knows what is going on with a player/coach relationship so maybe there's been problems for a while.
He's a good enough player to get by without a coach - I mean it's not like a guy can teach him anything about the game.