The 29-year-old will now join Pakistan's Babar Azam as Somerset's second overseas signing.
The duo last played for New Zealand in 2018 when the Kiwi side faced Pakistan in a T20I.
As per selector Gavin Larsen, the World Cup door remains open for the injury-plagued duo provided they are able to prove their fitness and form.
Key for India, according to Santner, will be the spinners’ contribution in the middle overs.
Corey Anderson was not selected on account of an injured heel sustained during the last match and will fly back to New Zealand.
Hafeez added 34 quickfire runs with Shoaib Malik (10) as Pakistan romped home with two balls to spare.
While Pakistan have a 14-2 record in 2018, New Zealand have won three of 10 games this year.
New Zealand A's last one-day match against Pakistan A is on October 26, after which the additions to the Black Caps' ODI squad will be named.
New Zealand A will officially open their tour of the UAE on Friday when they face Pakistan A in Dubai.
With the World Cup approximately eight months away, Anderson has decided to opt out of first-class cricket competition to give himself a chance.