Cricket: Kane Williamson supportive of David Warner and Steve Smith after ball-tampering ban

On the eve of his side's first test against Australia, Black Caps captain Kane Williamson has gone into bat for two of his main rivals.

Williamson has come out in support of Australian pair Steve Smith and David Warner after the duo were banned for 12 months for their roles in the infamous ball-tampering incident in Cape Town last year.

Warner and Smith have since been reinstated into the Australian test side, and after being given a hostile reception during the Ashes series in England, the pair have been largely well received by Australian crowds - support that has been backed up by Williamson.

"It (the ball-tampering plan) crossed the line, and the punishment was severe," Williamson told the Herald Sun.

"But it was heavy character assassination, and largely unfair. They made a mistake and they put their hands up.

"They're not bad people. They just pushed the boundaries and got a bit caught up with it in that moment."

Kane Williamson and David Warner are good friends. Photo / Getty

The New Zealand skipper said it would have been a "huge shame" had Warner and Smith been lost to the game.

"They've come back and it is truly great to have those guys back in the game of cricket and leading the way," Williamson said.

"They would've learnt a lot about it. For us, it's not something you'd obviously wish to be involved in, in any way whatsoever.

"You're always competing hard and obviously trying hard to take wickets. It was an unfortunate event."

The pair loom as the two key wickets for the Black Caps to claim in the day-night test in Perth starting tomorrow night, with Warner coming into the game off the back of scores of 154 and a record-breaking 335 not out against Pakistan, while Smith became the fastest batsman to reach 7000 runs, and averages an absurd 63.8 in tests.

Their best option to take on the dangerous duo would be Trent Boult, who has dismissed the pair four times apiece in six tests. However, Boult missed the most recent test against England due to a side strain, and Williamson revealed in his pre-match press conference that the seamer still needed to be monitored at the team's final training before a decision could be made on his availability.

Trent Boult still has to get through one more training to be ruled fit to play Australia. Photo / Getty

If Boult is unable to play, either Matt Henry or Lockie Ferguson would come in the starting XI. All-rounder Colin de Grandhomme, who also missed the second test against England, is set to be available however, while Ross Taylor will also play, despite a brief scare at training when he was struck on the thumb.