'What were you thinking?': Ian Smith baffled by Kane Williamson decision during Boxing Day test

Kane Williamson. Photo / Photosport

Ian Smith has added to the chorus of concern over New Zealand cricket captain Kane Williamson.

The former international wicketkeeper, who has become a major player in the world's TV commentary boxes, said he was baffled by aspects of Williamson's batting and captaincy.

Williamson was beyond reproach going into the three test series in Australia, but that has quickly change with his critics including former captain Brendon McCullum.

Smith told Cricket AM that one Williamson decision in particular "blew my mind".

"Australia have bowled well to him but he's made mistakes with the bat that I have not seen him make in his career to this point," Smith said.

"Particularly in this test match. The shot he made late on the second night was so un-Kane Williamson-like that it caught us all by surprise."

Smith thought the heat in Perth and Melbourne had played a big part in Williamson's struggles.

"I looked at him in Perth - he's a really traditional player in terms of in the field - he will always wear the black cap because he's so proud to where it and he leads from the front," Smith said.

"Over there I noticed on a couple of occasions he was wearing the white floppy hat. That was an indication to me that the extreme heat in Perth was getting to him.

"He was very red-faced, he looked tired and exhausted at times.

"The other thing is we're not getting any starts so there's a very small transition between being out there captaining and out there batting.

"That's the issue, it's wear and tear mentally as opposed to physically."

Smith said Williamson's state of mind was a "genuine concern."

"Some of the decisions he's been making in the field ... and when he brought out Tom Blundell to bowl on the first day it just blew my mind.

"What were you thinking about that? He's a wicketkeeper batsman and he's bowling on the MCG on Boxing Day. A real head-scratcher for me."