Black Caps all-rounder Colin de Grandhomme has been ruled out of the upcoming test series against the West Indies due to bone bruising in his right-foot.
He's been replaced by Daryl Mitchell.
Spinner Ajaz Patel's left calf tear has improved, but not enough to be available for the first Test starting next Thursday in Hamilton, with Mitchell Santner drafted into the squad as spin cover.
Santner, who is set to play the opening T20 against the Windies at Eden Park on Friday night after coming out of managed isolation this Thursday, has also been confirmed to become the eighth Black Caps T20 captain when he takes over from Tim Southee for the third and final match of the series at Bay Oval on Monday.
Coach Gary Stead confirmed the changes.
"The unavailability of Colin and Ajaz has obviously had a flow on effect to our T20 squad who are providing the replacement players for the Test squad," he said.
"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.
"They both proved last summer in the Tests against England what they can do in our conditions with Mitch scoring a century and claiming three wickets at Bay Oval, while Daryl produced a polished half-century on debut at Seddon Park.
"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 T20 wickets are the most by any Black Caps bowler since his debut and he is currently ranked sixth in the ICC T20 bowling rankings.