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Like one ball out of 10 or 20... :- )
It is true that some OF's don't read the spin of an unusually-slicing ball all that well, especially if they're not fulltime at the position (Cabrera and Milledge would probably qualify as less-experienced). Which is why you'll see a guy like Ichiro hesitating to move over.
Not sure how many of those balls occur, though.