Cricket: Former Black Caps captain Brendon McCullum takes aim at Kane Williamson's tactics against Australia

Kane Williamson's tactics have come under fire from former skipper and teammate Brendon McCullum. Photos / Getty

New Zealand skipper Kane Williamson is under fire from his legendary predecessor Brendon McCullum for his bizarre defeated tactics in the second session of the second test at the MCG.

Australian batsmen Tim Paine and Travis Head were gifted overs against New Zealand's third-string attack after the lunch break, including three overs from batsman Tom Blundell.

With Williamson resistant to bring spinner Mitchell Santner back on or bowl himself, the highly-regarded captain gave the rock to Blundell while trying to give his quicks a breather.

Unfortunately, the game had largely slipped through New Zealand's fingers by the time Williamson reacted and took Blundell out of the attack with 0-13 from three overs.

The period where the pressure valve was released on Head and Paine allowed Australia to cruise past 400 and Paine to reach his fifty.

"I think it's been a pretty poor session. I don't understand some of the tactics to be honest," McCullum told SEN Radio.

"It's just staggering. By all means, have a blast, but the game was still in the balance.

"To me it was a submissive move [to bowl Blundell at the start of the session]. I just don't understand it.

"They just rolled over."

Kane Williamson's tactics have come under fire from former skipper and teammate Brendon McCullum. Photos / Getty

Blundell had never bowled at test level before and McCullum questioned if the part-time wicket keeper even gets a chance to bowl during New Zealand training sessions in the nets.

Aussie great Damien Flemming told SEN Radio Williamson's decisions were "bizarre".

"This is bizarre. If that's his [Blundell's] stock ball, he's going to be slogged here," he said.

"What are New Zealand doing? They need another wicket and to get into the tail."

Aussie legend Adam Gilchrist told Fox Cricket New Zealand's bowling after he lunch break was "not good enough".

Commentator Tim Lane told Channel 7 the period after the lunch break was New Zealand's worst of the entire series.

"They've probably had their worst period of the series since Smith's wicket," he said.

"The door opened for them briefly and they haven't been able to cash in on that at all.

"Things are really getting away from them quickly now."