New Zealand have flown in Glenn Phillips as cover for the third Test against Australia following viral infections to captain Kane Williamson and middle-order batsman Henry Nicholls.
The move to include Phillips in the side denotes a lack of confidence in Jeet Raval's batsmanship as the opener has been sidelined after his failure in the first Test.
Raval's deep slump in form has seen him muster just 66 runs in his last nine Test innings as he lost his place in the side to Tom Blundell in the Melbourne Test.
Meanwhile, Phillips has been rewarded for his productive outings in New Zealand's domestic season.
The wicketkeeper-batsman, who has turned out for the Black Caps national side in 11 T20Is, has four centuries and nine half-centuries to his name in first-class cricket.
Phillips recently hit 116 against England for New Zealand A and is his side's third-highest run-getter in the 2019/20 Plunket Shield.
New Zealand head coach Gary Stead noted Phillips' adaptability would make it easier for the management to adjust him in the batting combination.
"Glenn has been in terrific form this season and has good versatility with where he can bat and the roles he can play," he said.
However, Stead stressed that the decision to call up the youngster was a precautionary move and expected Williamson and Nicholls to recover in time.
"We're still hopeful Henry and Kane will pull through and we will give them every chance to prove their fitness."
In addition to the illnesses contracted by the batting pair, all-rounder Mitchell Santner was also forced to miss the team's practice session on Thursday.
"It's up in the air at the moment -- a couple of boys are a little bit crook, unfortunately," said opener Tom Latham on the eve of the Sydney Test.
"They're having today off, as well as yesterday, so fingers crossed they'll be right to go tomorrow.
"It's gone around the team a little bit which obviously isn't ideal, but fingers crossed, they're resting up and hopefully they'll wake up tomorrow morning and be good to go."
Latham admitted Williamson's hunger to lead the side and salvage their pride after successive defeats by significant margins meant the veteran player would make the cut for the final playing XI.
"He's obviously a great leader amongst this group and he's passionate about this group," he said.
"If there's any chance of him paying, even if it's a small chance, he'll certainly be playing."
New Zealand face the prospect of being whitewashed in Australia, which would be a major blow to their standing in the World Test Championship table.