Yep, the only time you're allowed to have more than one player (or two in T20) in any XI not ready to play for NZ at a moment's notice is a Wagner-type holding period.
2. Overseas Player means a person who is not eligible to play for the Black Caps; and does not meet
the NZ Qualifying Player criteria.
3. NZ Qualifying Player is a player who:
a) has declared his intention, in writing to NZC, to become eligible to represent the
(b) is not currently eligible to be selected for the BLACKCAPS or available for selection
for another country‟s national team;
(c) has, immediately following his declaration played in New Zealand for two (2)
consecutive seasons and/or resided in New Zealand for a continuous period of not less
than 12 months; and
(d) continues to demonstrate his ongoing commitment to becoming eligible for the
BLACKCAPS to the satisfaction of NZC and the CPA.