"For example, and this is an extreme example, a rugby test is already happening and if it came to the major events fund then we'd say 'it's going to happen anyway'."
The fund had previously been used to help bring the Under-20 Football World Cup and the Rugby League World Cup to New Zealand.
Neither event would have gone ahead without Government backing, Joyce said.
State funding could also be contingent on whether local agencies were supporting the boxing event.
"When a lot of the benefit accrues to a particular city you would normally expect to see, for example, ATEED involved as well," Joyce said.
Potential good news for Duco is that the Auckland Council-backed ATEED has already shown willing. Chief executive Brett O'Riley told the Herald yesterday that he was "delighted" with the confirmation the fight would happen.
"It will be one of the most highest profile events that Auckland has ever hosted," he said.
"We definitely intend to be a major partner with them in the fight and we will work with Duco on that basis. We have already had some preliminary discussions.
"This will be a major event so we will need to sit down with Duco now and see what kind of assistance they are looking for, both in cash and in kind.
It will be in the hundreds of thousands, balance between cash and services still to be determined."
Eden Park is one of the front-runners in terms of venues. There is potential to set up a covered ring in the middle of the pitch, and a major plus would be the capacity - about 59,000.
However, Eden Park chief executive Guy Ngata told Radio Sport yesterday that the limited notice provided challenges.
"Fifty days to sell out 50,000 seats is not long at all. It's a really high-risk proposition and I guess from our point of view it's about mitigating that risk as best we can.
"We're hopeful and we're having further discussions next week, but we'd like to think it's not the last opportunity we'll have of hosting a Parker title fight."
A late finish would present problems due to Eden Park's residential status, but Ngata said the fight could be held in the afternoon to cater for the East Coast USA television market.