Williams has previously suffered defeat at the hands of a US prodigy at Melbourne Park , beaten by teenager Sloane Stephens in the 2013 tournament .
Williams has previously has never been thrown off the top of the heap by year 's end .
Williams has previously suffered defeat at the hands of a US prodigy at Melbourne Park , beaten by teenager Sloane Stephens in the 2013 tournament , but has never been thrown off the top of the heap by year 's end .