Mitchell Santner is set to be ruled out of the Black Caps' test series against Pakistan because of a fractured wrist.

Black Caps all-rounder Mitchell Santner may miss this month's test series against Pakistan due to a fractured wrist, and it's now the New Zealand selectors' heads which will be doing the most spinning.

Santner, who has quickly become the country's No 1 spin bowler, suffered the injury at Northern Districts training on Friday, and is likely to be sidelined for three to four weeks.

"After such a strong tour of India, it's really disappointing for Mitch to pick up this injury ahead of the first match of the home summer," said NZ coach Mike Hesson.

"We're unsure whether Mitch will be available for the second test at this stage, but we'll be monitoring his recovery closely and look forward to having him back."

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The first test against Pakistan begins on Thursday 17 November at Hagley Oval in Christchurch, with the second test starting at Hamilton's Seddon Park on November 25.

Santner was one of five Black Caps returning to the ND side for their Plunket Shield match against Canterbury in Hamilton, starting Saturday, and was struck on the hand while batting in the nets on match eve.

Despite batting on after the blow, he was sent to hospital for scans. ND coach James Pamment confirmed Santner's x-ray had detected a small hairline crack in his right (non-bowling hand) wrist, and he was later wearing a cast.

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The 23-year-old had been one of the few positives from the recently-completed Indian tour, where he played all three test matches and five ODIs, scoring his maiden test half century and showing a real ability to tie up and end with his accurate tweakers.

From 10 tests he has a batting average of 23.46, has taken 25 wickets at 38.48, and is a superb athlete in the field. His injury leaves the Black Caps' selectors in a conundrum ahead of the two-test series against Pakistan, which starts in Christchurch on November 17, and concludes with the second match in Hamilton from November 25.

Santner was set to have been the sole spinner for the series, and now this weekend's meeting between Hesson and co-selector Gavin Larsen may be a bit longer than they had anticipated, as they look to finalise their lineup for the series.

Off-spinner Mark Craig is still sidelined with a side strain which ruled him out of the second and third tests against India, while fellow off-spinner Jeetan Patel and leg-spinner Ish Sodhi are other options, having also played on the tour.

However, it may be leg-spinner Todd Astle who roars into the equation for a surprise return to the side. The 30-year-old Cantab played his one and only test in 2012, in the win over Sri Lanka in Colombo, and his superior batting may well see him win the nod.

Astle has also been named in the New Zealand A side to face Pakistan in a three-day match in Nelson, from November 11, having been in tremendous form to start the Plunket Shield season - scoring 262 runs at 65.5 and taking 11 wickets at 21.18.

"He's knocking the door down," Larsen had said of Astle. "Todd hasn't put a foot wrong for the best part of a couple of seasons now. He's raced out of the gates again, and just keeps pushing his name forward. It would be remiss of us not to be seriously including him in discussions."

Santner's injury may yet have further implications for the Black Caps, as he could be touch and go for the three-match Chappell-Hadlee ODI series in Australia, which starts on December 4.

It continues some recent bad luck he's had with his hands. In November last year he suffered a fractured little finger on his bowling hand in training, though was able to make his test debut in the historic first day-night test, against Australia in Adelaide, just days later.

Then, in May this year, he had to fly home from his stint in England with Worcestershire after just one game, having broken a finger while fielding, and then requiring an operation because there was a complication in the healing process.