New Zealand added former Sri Lanka spinner Rangana Herath and India's ex-batting coach Vikram Rathour to their coaching staff on Friday for their upcoming three test matches in Asia.

New Zealand play a one-off test match against Afghanistan in Greater Noida, near Delhi, from Monday before flying to Sri Lanka for a two-Test series in Galle.

Herath was roped as spin-bowling coach Saqlain Mushtaq left to take over a mentor's role in new domestic competitions introduced by the Pakistan Cricket Board this season.

"We're really excited to introduce Rangana and Vikram into our Test group," New Zealand coach Gary Stead said.

"Both men are held in high regard in the world of cricket and I know our players are really looking forward to the opportunity to learn from them."

Working with Herath, Test cricket's most successful left-arm spinner with 433 wickets from 93 matches, would benefit Ajaz Patel, Mitchell Santner and Rachin Ravindra, said Stead.

"For our three left-arm orthodox spinners in particular, Ajaz, Mitch and Rachin, having the chance to work with Rangana across three Tests on the sub-continent will be hugely beneficial.

"Rangana has taken over 100 Test wickets in Galle which is the venue of our two tests against Sri Lanka and so his knowledge of that venue will be priceless," Stead added.

After the series in Sri Lanka, New Zealand will return to India to play three Tests against Rohit Sharma and his men.