Mullins said Ferguson's success was no surprise as "he's been pretty much right at the doorstep challenging [other shearers]," throughout the season.
"He had a fabulous show in Waipukurau, he did well at Golden Shears. So there's always just that element of ... you just don't know."
Ferguson was not only up against Smith, but Scotland international Gavin Mutch, and world teams champions Nathan Stratford and John Kirkpatrick.
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All four men "wanted it badly," as they battled it out for a place in the World Championships said Mullins.
Ferguson's success was extraordinary as he almost lost a sheep over the side of the board said Mullins.
"From a competitive perspective that would've just been enough almost to knock your head into a different place."
Also in today's interview: Mullins discusses other winners at the Shearing Champs and a recent Agri-Women's Development Trust course.