New Zealand are waiting on the fitness of Tim Southee ahead of the second Test against England, which starts at Old Trafford on Friday.
The 19-year-old seam bowler sat out training on Wednesday due to a virus that has decimated his energy levels.
"He's had a bug for the last 24-48 hours," confirmed Black Caps coach John Bracewell.
"His energy levels have been down and his food has been up!
"We will see how he comes through the next day or so. His energy levels are so far down we didn't want to risk have him practicing and pushing his levels down even further."
Southee, who has played just two Tests, went wicketless in the drawn series-opener at Lord's but was expected to retain his place for Manchester.
Should he be ruled out, New Zealand have plenty of alternatives in their squad. Seam bowlers Michael Mason and Iain O'Brien appear the most likely candidates, while off-spinner Jeetan Patel would also merit consideration.
Bracewell is not concerned by the 'workmanlike' tag that has been applied by some to his squad, adding that they are full of confidence after Jacob Oram's century helped them bat throughout the final day to secure a draw at Lord's.
"Workmanlike, yeah, but having said that Jacob's and Brendon's (McCullum) innings (97 on the first day) showed a little bit of style and class as well," he noted.
"I certainly don't mind that tag and crafting out results - there is nothing wrong with a good work ethic.
"We had to be prised out on the last day, which is something we've been looking for over the last couple of years.
"The adventure of England in itself still has that traditional tag as the tour of choice.
"It still has a number of warm-up games, you go on the coach everywhere rather than jet in and out of places, and the pace of it gives you that opportunity to bond as a team in a relatively safe environment.
"New Zealanders still relish this as the tour to be on, so it is tough to get a place on the coach via performances in our domestic season."