New Zealand head coach Gary Stead said Kane Williamson's injury could be made a case study, such is the rarity of the captain's pectoral problem.

Williamson suffered a grade one pectoral muscle tear as the Black Caps crushed Bangladesh by an innings and 12 runs to seal a Test series win in Wellington on Tuesday.

The skipper scored 74 runs to help New Zealand reach 432-6 declared in the second Test on Monday but Williamson was nowhere to be seen at Basin Reserve 24 hours later.

Williamson is in doubt for the third and final Test in Christchurch and while the injury is not major, it has left Stead and the Kiwis scratching their heads.

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"They've only seen five in the world before. It's very minor but we're hopeful he will recover quickly," Stead told reporters post-match.

"The physio and staff were saying we'd make this a case study because it is so rare. It's like any muscle, there's irritation and a wee bit of bleeding but it's not a major injury.

"We're hopeful in a short period of time he'll be back to full noise."

Injury update: Williamson in doubt for the third Test after an MRI confirmed a grade one tear to his left pectoral minor muscle. He will travel to Christchurch with us to be further assessed. The third Test starts on Saturday. #NZvBAN pic.twitter.com/ca83KFarb2 — BLACKCAPS (@BLACKCAPS) March 12, 2019

Stead continued: "If he's fit, no player wants to give up their spot in the test team. It's safe to say we'll probably err on the conservative side and if there's any chance of risk then we're likely to pull him from that game."

Two full days of play were lost to rain in Wellington but New Zealand still managed to bowl out Bangladesh for 211 and 209.

Neil Wagner (5-45) and Trent Boult (4-52) tore through the tourists' batting line-up on the final day, with Bangladesh all out before lunch as the Black Caps locked up second spot in the ICC Test rankings.

"Fantastic performance," Williamson said. "We needed to score quickly to have a chance to win here. It was about playing good cricket.

"We were under some pressure after the first day. I think Bangladesh bowled well in the first wicket without much luck."