"I highlighted last week how tight and complex the schedule was - so when you throw in some injuries, it really begins to challenge how you juggle your resources.
"Mitch and Daryl will be available for the final T20 game, before linking up with the test squad on Tuesday where we will monitor them closely to ensure they're fit and fresh ahead of the first test on Thursday.
"I'd like to acknowledge Mitch Santner for taking on the responsibility to captain the T20 side. It's a great honour to lead your country and I know his calm demeanour along with the sheer amount of international experience he's amassed in the past five years will hold him in good stead.
"With just two days between the two series, we've made the decision to have our T20 players, who are also test regulars, assemble in Hamilton on the Monday and that reflects our focus on the World Test Championship.
"It's disappointing for Colin to be ruled out of the tests completely and he'll now target being fit and available for the Boxing Day test at Bay Oval.
"Ajaz will join the team in Hamilton to have treatment and train. We will make a call on the second test in Wellington closer to the time."
Since debuting in 2015, Santner's played 138 times for the Black Caps, including 44 T20 internationals.
His 52 T20I wickets are the most by any Black Caps bowler since his debut and he is ranked sixth in the ICC T20 bowling rankings.