Kane Williamson's tour of Australia has taken another hit, with the Black Caps captain absent from training today with flu-like symptoms.
Williamson, who has made just 57 runs in four innings so far on tour, and has come under criticism for his captaincy decisions, missed the Black Caps' first hitout at the Sydney Cricket Ground ahead of the third test, which starts on Friday.
Nicholls has mustered returns of 7, 21, 0 and 33 in his four innings in Australia, and hasn't passed 42 in his last nine test innings.
However, he too is crucial to New Zealand's chances in Sydney, with the Black Caps possessing seriously limited options in terms of available batting cover.
Horrendously out-of-form opener Jeet Raval is the only batsman waiting in the wings, with bowlers Todd Astle, Kyle Jamieson, Matt Henry and Will Somerville the other squad options who didn't play in Melbourne.
Despite their absence today, Black Caps bowling coach Shane Jurgensen was confident that Williamson and Nicholls - who both turned up to training before being sent back to the team hotel to avoid any symptoms spreading - would be fine for the final test of the tour.
"They're just not feeling really good today, I'm sure they'll be back training tomorrow, they're pretty tough. It's been a big last two tests so I think it's just a good opportunity to have a day off and they'll be here tomorrow."
Williamson's potential absence would be the biggest blow, even though the skipper is currently in the midst of his worst return over a four-innings stretch since the disastrous tour of South Africa in January 2013, where New Zealand were infamously rolled for 45 on their way to two heavy defeats.
Had Joe Denly not committed one of the worst drops in the history of cricket when Williamson was on 62 against England in Hamilton, Williamson would be averaging just 19.8 in his last 10 innings, and his captaincy is coming under closer scrutiny as well.
Williamson's decision-making in the field has been criticised during the lengthy spells the Black Caps have been forced to spend in the scorching sun – including criticism from former skipper Brendon McCullum, who suggested he wasn't enjoying being captain as much as he had in the past.
Jurgensen believes that having an extra day away from the grind of the tour could potentially be helpful for Williamson.
"I'm sure Kane would have struggled to go home, he loves batting – he'll be thinking about his batting," Jurgensen joked.
"When you've had a couple of tough losses, it's good to get a bit of extra time away whenever you can – it's not always the best to keep working hard and working hard. So it's a good opportunity for him to take a bit of time out and reflect and have a big last test to finish off the tour."
Australia's standout seamer Pat Cummins believes the Black Caps' danger in Sydney could come from the likes of Williamson and Ross Taylor, both of whom struggled in Melbourne.
"You've always got to be wary – especially a high-class team like New Zealand. They're number two in the world for a reason, they've got some really high-quality batters that probably haven't fired yet, so they're the ones to watch out for I reckon.