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Williamson did not field in Bangladesh's second innings, after injuring his left shoulder while diving in the field in the first innings. He had experienced pain while batting, and subsequent scans revealed that he had suffered a grade one tear to his left pectoral minor muscle.
Remarkably, Black Caps coach Gary Stead said it was an injury that had only been seen five times worldwide.
"It's a pretty rare injury – they've only seen I think five in the world before.
"I know that the physio staff were saying 'We'll make this a case study' because it is so rare."
That, naturally, would lead to concern about Williamson's fitness, as well as potential uncertainty about how to heal the injury, but Stead is optimistic that his captain will have a simple recovery.
"It's very minor but we're hopeful he will recover quickly.
"Kane's managed his way through injuries before, he's had niggles all the time, and he seems to find a way through. The extent of this and the unknown of this were the things we were unsure about, but hopefully, he'll get through that fine.
"It's like any muscle, there's obviously irritation and a wee bit of bleeding, it's not a major injury, so we're hopeful in a short period of time, he will be back to full noise."
'Hopeful' might be the operative word, and while Williamson is set to travel with the team to Christchurch for the third and final test, Stead indicated that he will only play if he's completely fit.
"The thing for us over the next 48 to 72 hours is just to make sure he doesn't aggravate it any more.
"If he's fit, no player wants to give up their spot in the test team. But I think it's safe to say that we will probably err on the conservative side, and if there's any chance of risk then we're likely to pull him from that game."
If Williamson is ruled out then Central Stags batsman Will Young will be in line to debut for New Zealand.
"Will has been in our test squad as batting cover for the past two series and he should be confident following some strong performances domestically and for New Zealand A."
Stead also provided an update on wicketkeeper BJ Watling, who hurt himself while warming up before play at the Basin Reserve on day five.
"BJ has a minor left hamstring strain and we felt it was best he didn't keep today to give him the best chance of being fit for the third test."
Northern Districts wicketkeeper Peter Bocock, one of two substitute fielders for New Zealand, took the gloves in Watling's absence.
A decision on any replacement players for the 13-man squad will be confirmed at the conclusion of the latest round of the Plunket Shield.
While the World Cup in May is an obvious focus, Williamson still has the matter of the lucrative Twenty20 Indian Premier League to worry about, with the 28-year-old set to link up later this month with the Sunrisers Hyderabad.
Stead is confident that Williamson will be fit in time but stressed that New Zealand Cricket won't let the Indian franchise take any risks with their star batsman ahead of the World Cup.
"From what I've been speaking with the physio and Kane about, if things progress as we hope, then going to the IPL shouldn't be a problem for him. But he's also aware that if he's not quite 100 per cent, then we will potentially hold him back as well and make sure he is right before he goes on that plane."