England may hold the No.1 spot in the world Test cricket rankings but New Zealand batsman Kane Williamson believes the Proteas are the real top dogs.

The 21-year-old, who battled for four hours and 13 minutes to make 77 in the second Test in Hamilton, believes the team that thumped them by nine wickets deserves to be called the best in the world.

“We know what we’re up against and it’s probably the best team in the world at the moment,” he said looking to the third Test in Wellington which starts on Friday.

Williamson had struggled for runs this summer and the way he fought after coming to the wicket with the score at 3-7 won praise from captain Ross Taylor after the defeat.

“A lot of guys wouldn’t have handled it (the situation) as well as he did,” Taylor said.

Williamson, who scored 131 on his Test debut against India in Ahmedabad, says his lengthy vigil at the Seddon Park was his toughest examination in his burgeoning Test career.

But he admits the bouncy Basin Reserve pitch will provide South Africa’s potent attack another chance to give him a working over.

“There’s another challenge ahead in Wellington on a different surface so my preparation will be around that sort of track and how to combat their bowlers on that wicket.”

The Black Caps, dismissed for 185 and 168 in Hamilton, have added batsmen Dean Brownlie and Daniel Flynn to their squad at the expense of opener Rob Nicol and seamer Brent Arnel.

But whoever takes the field in Wellington, Williamson says they have to be at their very best if they stand a chance of squaring the series.

“We know we have to bring our `A’ game to really compete. We showed glimpses of it in Dunedin and in Hamilton we fell a bit short. But we know we can do it and we need to keep that belief that we can do it in the next game.”