I think Brown can totally win this. Both guys have had some rough spots recently in their careers and are crowd pleasing to watch. Brown is the better well rounded fighter and I think will this either by sub or (T)KO.
Top 5 is a huge huge stretch. The people in the top 5 are above and beyond better than Matt Brown. He could stay in the top 10, but I can't think of a single person that would be considered a top 5 WW that Brown would even almost beat.
Just curious who are your top 5 at WW?