My point was, you can still be a great fielder and only rank 10-13th. QA kid who scores 99 for a semester but is ranked 3rd out 5 is not mediocre.
I agree that JBJ can eventually be replaced and maybe should be, if he can't hit over somewhere around .600 to .650. Once he gets to the .650-.700 range, it's more debatable. If he's over .700, IMO, he's a clear plus that can still be improved upon, but show me who and how before I say yes.
Clearly, if he hits .500 this year, we can find a great glove CF'er for cheaper than JBJ's arb (even though that might not be that much after a .500 season).