Siddle a concern ahead of second Test

Australia's attack is far from settled as they prepare to hunt the No.1 Test ranking in Christchurch, with Peter Siddle in doubt for the New Zealand tour finale.

Siddle suffered back spasms on day three of the first trans-Tasman Test, which Australia won by an innings and 52 runs in Wellington.

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The 31-year-old delivered the final over before tea on Sunday but did not bowl again in the Basin Reserve clash.

Skipper Steve Smith insisted Siddle could have bowled on Monday if he was needed.

The second Test starts on Saturday and Smith acknowledged Siddle's setback was something that needed to be closely monitored this week.

"He's had a bit of spasm through his back," Smith said.

"I was able to keep him on ice. He wasn't needed in the end.

"We'll wait and see how he pulls up over the next couple of days to see whether he'll be fit for that second Test match."

James Pattinson looms as an obvious replacement, provided he can convince selectors and team medical staff that he is fully fit.

Pattinson missed a month of cricket following the New Year's Test in Sydney because of shin soreness and the lack of match fitness cost him a place in Australia's XI at the Basin.

"He's done quite a lot of bowling this week. He's had quite a few sessions," Smith said.

"I saw him bowl this morning actually and it looked like they were coming out pretty nicely and quite fast.

"He's tracking pretty well to be fit for the next Test match."

Jackson Bird, playing his first Test since the 2013 Ashes, went wicketless in NZ's first innings but bowled better in their second dig.

Uncapped South Australian Chadd Sayers is the other pace option in the squad.

Australia's pace depth has been severely tested over the past eight months.

The retirements of Ryan Harris and Mitchell Johnson have hurt, while Mitchell Starc is still on the sidelines because of ankle surgery.

Pat Cummins and Nathan Coulter-Nile weren't considered for the two-Test series in NZ because of injuries.

Siddle was restricted by back spasms earlier this summer in the inaugural day-night Test at Adelaide Oval.

The Victorian was passed fit and played the following Tests in Hobart and Melbourne but an ankle injury forced him to miss the SCG Test.

Outgoing NZ skipper Brendon McCullum showered Australia's bowlers with praise after his side's first Test loss at the Basin since 2010.

"Their bowling was world class," McCullum said.

"You know when you've got favourable conditions it's not always easy to execute as well as they did for as long as they did.

"Nathan Lyon bowled brilliantly too."

Smith agreed.

"We hit good areas, we built a lot of pressure and the bowlers reaped the rewards," he said.