The spectacular knockout didn't come, despite Parker putting Bergman down in the second round with a left hook to the head and in the seventh with a left to the body. It was a dominant performance - Bergman admitted Parker won every round - but the TKO in the eighth round was a more a result of attrition than anything else.
"I was a little slack with the jab a few times ... but again, I got a little too close and didn't give myself enough space to throw the punches to ... do the damage," a sweat-soaked Parker said afterwards.
"I probably started on the body a bit late."
Trainer Kevin Barry said: "He did get a little frustrated and that's part of the learning curve, it's something that we're going to have to work on - to stay composed and not get frustrated during longer fights.
"He's had some great knockouts and he wanted to have a spectacular knockout in Samoa and he probably tried a little too hard."
Parker was caught with a left-hand lead by American southpaw Bergman in the first round, a shot that seemed to surprise the 24-year-old Kiwi.
The counter-punch was followed with a taunt from the tough 31-year-old from Pittsburgh, an indication of his defiance which kept him in the fight for longer than many expected.
Parker said: "He said 'you're a big guy with good speed but you're not hurting'. When I got back to the corner Kev said 'don't worry about what he's saying, get back with the plan'."
In the end Bergman couldn't sustain the battering. There was no disappointment on his face when the referee called it off and his bruised and swollen face told its own story.
"I couldn't believe how durable he was," Barry said. "He came to survive, he had those blinkers up constantly. He knew that Joe was a powerful guy but I was really surprised that he lasted the time that he did, especially with the body shots that he absorbed."
Bergman was reluctant to compare Parker with WBC champion Deontay Wilder, with whom he has been sparring, but said: "He's a strong hitter, he throws good combinations, but I honestly believe he's got a bit more development [to do] yet.
"I give Joseph credit, he's got a good chin. I caught him with a good shot and everyone saw that he felt it."
Duco promoter David Higgins, who travelled to Samoa six times in 12 months in preparation for the event, said he had approached the week with "trepidation" in terms of the financial result, but added: "We're certainly not going to get rich out of it but it's been more successful than we had anticipated."