Hansen was also an assistant to his predecessor, Graham Henry, but Foster comes into the job in very different circumstances.
The team Hansen took over had just ended New Zealand's long wait for a second World Cup triumph and boasted the talents of all-time greats Richie McCaw, Keven Mealamu, Tony Woodcock, Conrad Smith, Ma'a Nonu and Jerome Kaino.
That core group stayed on to keep the All Blacks top of the world rankings and won the Webb Ellis Cup for the third time in 2015 before all but Kaino ended their international careers.
