Fa's manager Mark Keddell said Fa suffered an 'internal issue'.
"It's about getting Junior back in the ring as quick as possible," Keddell said.
"Everyone is very confident that things will go well. Short of catching Covid in the hospital, we'll be happy days."
Keddell on Friday said he was not in a position to give any more details about what the test revealed or what the surgery entailed, saying in this game there were cards you had to keep close to your chest.
"Junior's essentially had an injury and he's going to have a routine operation," Keddell said, and, while the news was "devastating", he didn't see it affecting his fighter's chances.
"He's in amazing shape," Keddell said. "He's at his fight weight, he's got a six pack, it's just one of those things."
Keddell said while Fa will lose some aerobic conditioning during the lay-off, he was coming from a strong base and his power will only increase during the break.
Duco owner and Parker's manager, David Higgins, on Friday notified sponsors, broadcasters and key stakeholders about the decision.
"It's one of those things where you just have to roll with the punches, if you'll excuse the horrible pun," he said. "Boxing has a long history of this and often the delay creates even better events. You've got to look for silver linings."
Higgins cited the Rumble in the Jungle and our very own David Tua-Shane Cameron clash as events where delays added to the anticipation. Both ended up being, on vastly different scales obviously, cultural phenomena.
The fight was being sold pay per view on Spark and was primarily backed by the Chow brothers' Stonewood Homes.
"It's business as usual," Higgins said. "All tables and ticketing remain valid. There is a waitlist for tables so those that might not be able to make it, their tables will revert to those on the top of the waitlist.
"We're also working with Air New Zealand to help those flying to the fight who have been affected."
The fight is important for Parker (27-2) who has strung together three wins of varying quality since losing back-to-back bouts with Britons Anthony Joshua and Dillian Whyte.
If it was important to Parker it was critical to Fa (19-0), who at 30 has not gained the traction in the heavyweight rankings that his unbeaten record suggests he should have, due mainly to the nondescript quality of most of his opponents.
While the Fight of the Century puff is pure boxing hyperbole, it is not an exaggeration to say this was a career-defining fight for Fa and a career-crossroads match for Parker.
"Joseph is in terrific shape," Higgins said. "After close to a year of training and waiting, I imagine Joseph will have some fury to unleash on Junior Fa when they get in the ring next year."
The fight was not just highly anticipated as a sporting contest but also as a boost to an events industry that has received a standing eight count as a result of the pandemic that has wormed its way across the globe.
Several high-profile sports events and festivals have already been cancelled this year, including the ASB Classic, the Piha Pro surfing contest, and music events like Laneway.