Jos Buttler is a serious injury doubt for the second Test in Hamilton after suffering a back spasm in training.

Joe Root has confirmed that Ollie Pope will keep wicket if Buttler is, as expected, unable to play.

That would be a big ask of Pope. He has kept in just five first-class games, the last of which was in February. Rory Burns, England's opening batsman, has also kept wicket at first-class level, but not since 2014. Pope is expected to bat at No. 7 if he keeps wicket.

"Jos has tweaked his back in the gym," Root said. "We'll have to find out a little bit more information on that throughout today and see where he's at."

The obvious replacement for Buttler is Kent's top-order batsman Zak Crawley. He is 21 and averages a modest 31.27 in first-class cricket. But he has looked impressive all tour, scored a century in the only innings he has played and looks a terrific fielder.

Root also hinted that Chris Woakes could play. Not only could he come into the side instead of Buttler, but England are also understood to be considering dropping their spinner, Jack Leach, and utilising a five-man seam attack. While Leach was generally tidy in the first Test, his lack of bite was something of a disappointment. Certainly Mitchell Santner found more life in the pitch in England's second innings. Root looked England's most dangerous spinner at times at Bay Oval and, had Ben Stokes clung on to a chance at slip, would have dismissed BJ Watling for 31. Joe Denly, a part-time leg-spinner, has also been bowling in the nets and could be utilised if required.

The pitch at Hamilton also looks surprisingly green and, as of Thursday afternoon, a little damp. With an appreciable covering of grass, it would be no surprise if the captain winning the toss asked the opposition to bat first.

"There's a number of different combinations we could go with and I think a lot of that will rely on the surface," Root said. "Trying to find the best combination which would take 20 wickets and then balancing that in terms of getting the batting where we want it to be. It could be an allrounder, we'll see."

Realistically it seems Buttler is unlikely to play. England will be reluctant to go into a Test with a question mark over the fitness of a key player meaning Pope is likely to take the gloves. He enjoyed an extended session with Bruce French, England's keeping coach, at training on Thursday.

While Pope is a relatively inexperienced keeper, England dismissed the idea of calling-up a last-minute replacement; Ben Cox of Worcestershire, for example, who is currently playing Grade cricket in Adelaide. Not only would it have proved tricky to get someone to New Zealand in time, it would have been asking a lot of them to acclimatise to the conditions and the unique team environment. It might also have undermined the position of Pope who was selected as reserve keeper in the original tour party.

"We knew that this was a possibility when we selected the squad," Root said. "I'm quite happy that Popey's got the capability of doing a good job for us."

If Pope and Crawley perform well, it could have repercussions for Jonny Bairstow. There had been an expectation that Bairstow would win a recall for the South Africa series but, with England likely to pick a 16-man squad and Crawley having an opportunity to make himself impossible to drop, that may not prove to be a formality.

"You can't rule out anything out," Root said. "For Jonny, you look at his talent and what he's achieved in Test cricket and what he potentially could achieve in Test cricket and you probably think he's got the capability to go on and make really big scores and be one of the best players in the world as a batter alone."

Training was voluntary for England on Thursday. Only Buttler and Jofra Archer did not take part in the football that traditionally starts the training sessions, with Archer taking the opportunity for a little more rest after his exertions in the first Test.