Buttler tweaked his back during a gym session
England wicketkeeper Jos Buttler is an injury doubt for the second Test against New Zealand which starts on Thursday at 22:00 GMT.
Ollie Pope is on standby to take his place behind the stumps, with Kent batsman Zak Crawley a possibility to come into the side and make his debut.
"Jos has tweaked his back in the gym," said England captain Joe Root. "We'll have to see where he's at.
"We knew this was a possibility when we selected the squad."
He added: "I'm quite happy that Popey's got the capability of doing a good job for us."
Surrey's Pope, 21, has kept wicket in just five first-class games and would bat at number seven if he did take the gloves.