Both fighters, who are Tamatea rugby teammates, will aim to weigh in around the 93kg mark for the fight which is scheduled for five five minutes rounds.
"That's up another weight division for me. My first national title was won as a 74kg class fighter, my next one was at 77kg and my last one was at 84kg," Digby, who has a mixed martial arts win-loss record of 17 and 4, explained.
"I'm expecting a tough time. We're both well known fighters who want to do the best we can in all forms of combat sports ... in addition to the national title which is up for grabs, it's an opportunity to be the best in the Bay and I'm sure the crowd will love the fight," Digby, 31, said.
The Orphans Gym fighter works fulltime for Pro Fence Fencing but will still put in 10 hours of training each week leading up to the fight.
Haraki, 37, first got into the mixed martial arts scene as a kickboxer. However, this year he has been turning out on the Professional Boxing Association circuit in Auckland.
In his debut Haraki lost to the New Zealand Cruiserweight champion Monty Filimaea who fights out of the David Tua Gym in Auckland.
"I converted to boxing when I discovered it was becoming hard to find a mixed martial arts fight," Haraki explained.
In November last year he went to Amsterdam to train and fight with some of the best European fighters including Moroccan-Dutch super heavyweight Badr Hari.
"I was blown away by the calibre of the fighters there. During a sparring session I was cut just below my right eye with a knee ... it required three or four stitches and I came home sooner than expected," Haraki said.
"My last mixed martial arts fight was in August last year. It's going to be tough taking on Dan ... he's regarded as a veteran in the fighting game."
Haraki has another cruiserweight professional boxing bout on May 23, against Tauranga's James Emerson in Auckland.
"I'm 100kg and I've got to take a big cut to get down to 90kg for that one."
"I try and keep myself in shape because as you get older the recovery takes a bit longer," Haraki said.
A two-time Hawke's Bay premier rugby league winner's medal recipient (once with Tamatea and once with EITSA), Haraki plans to fight for another two years before becoming a fulltime trainer.
"My long-term goal is still to start my own gym. I want to pass on my knowledge to up-and-coming fighters," Haraki added.