Australia captain Michael Clarke thinks South Africa will definitely miss Jacques Kallis in the upcoming Test series between the sides.
However, Clarke says his team will still face an extremely tough challenge against the top-ranked Test side in the world.
Fresh from their 5-0 Ashes hammering of England, Australia are off to South Africa for a three-Test series, the hosts' first since legendary all-rounder Kallis retired.
And Clarke said: "I don't think you can replace Jacques, I think he is a once-in-a-generation player.
"To be able to bat, bowl and field as consistently as he did over such a long period of time? He is irreplaceable, there's no doubt about that.
"But, South African cricket is quite strong in their domestic cricket, so they will have a number of guys looking towards the position that is vacant.
"And the rest of the South African team is very strong. They bat very deep, especially if they have got AB de Villiers keeping. That means they can have an extra batsman at number seven.
"And they have got a lot of experience and class with the ball as well, hence they are the number one Test team in the world."
You can watch day one of the first Test from Centurion on 12 February, from 8.30am on Sky Sports 1.