Mitchell ruled out of second South Africa Test and Australia T20Is

Daryl Mitchell has been ruled out of the second Test against South Africa and the T20I series against Australia in an attempt to recover from a long-standing foot injury.

Mitchell, who averages 53.46 in Tests, has been carrying the problem for around six or seven months and was rested from the final T20I against Pakistan in January, but it has been decided he needs a longer period on the sidelines to give himself the best chance of being fit for the two-Test series against Australia.

"We took the opportunity to rest him a little earlier but after seeking medical advice on this as well it's likely that he needs a longer period of time," New Zealand coach Gary Stead said. "It's really tough, because there's not a lot breaks coming up in the next wee while so thought this gives us nearly three weeks to try and give him the chance of the best recuperation from it.

"There's no guarantees this will still work in that period of time but we are very hopeful that it will improve his chances of getting through a longer stint with us."

New Zealand have not called up a replacement for Mitchell with Will Young the spare batter in the squad and he could come in as a like-for-like swap. However, there remains a chance the side may be rebalanced with Glenn Phillips and Mitchell Santner moving up the order and another pace bowler brought in with Stead confirming the uncapped Will O'Rourke remained in contention for a debut.

"[Will Young] is definitely one of the options," Stead said. "Will's there as back up [and] Glenn Phillips has shown he's more than useful and it could be shaped differently. We are very happy with the squad we have. Daryl's obviously a huge loss, though, he's been instrumental in a number of outstanding batting performances but it's important for him and us that we get this right long term."

Meanwhile, Kane Williamson is unlikely to be available for the T20Is against Australia - a format where he is captain - as his wife is expecting their third child. However, Trent Boult could come into consideration for those matches with the left-arm quick not having any franchise commitments at that time.

"Trent's available if we want to select him," Stead said. "Him and I are still having conversations…hopefully in the next couple of days to nail down what that looks like."