McCullum was expected to play for Otago at Queens Park in Invercargill on Sunday against Wellington.
Instead, he will be turning out for New South Wales at the Telstra Stadium in Sydney tomorrow night in the final of the Australian twenty/20 competition.
The big hitter is playing for the Australian side so he can guarantee himself a chance of playing in the $US6 million ($NZ11.5 million) Indian Champions League in October.
By playing tomorrow night, McCullum will qualify as a member of the NSW team, which has automatically qualified for the league.
Each member of the team which wins the Champions League is expected to pocket about $NZ160,000.
Cricket New South Wales chief executive David Gilbert confirmed the signing yesterday was for the Indian tournament.
"With the potential losses the New South Wales squad may suffer, depending on which two Indian Premier League teams qualify for the Champions League, it is vital we strengthen our squad ahead of that tournament," Mr Gilbert said in a statement.
McCullum (27) plays for the Kolkata Knight Riders in the Indian Premier League, but that side is not guaranteed a place in the Champions League.
McCullum could not be contacted yesterday, but the decision to allow him to play in Sydney was backed by his Otago cricket boss.
Otago Cricket Association chief executive Ross Dykes said the move, instigated by NSW, fitted nicely with events.
"Circumstances allow this. It suits us and suits Brendon and suits New South Wales," Mr Dykes said.
"Potentially, we are talking about hundreds of thousands of dollars, but that is what comes with being a professional cricketer, and that is what Brendon is."
McCullum has agreed to donate his Sydney match fee, believed to be more than $5000, to junior cricket in Otago.
Mr Dykes said people could be cynical about the move and the money involved, but sport was in a professional age and cricket was one of the most professional of sports.
"Money makes the game survive. I can't be a stick-in-the-mud administrator when these sort of things are happening."
