Whittaker proceeded to bench 230kg and deadlift 325kg for a combined total of 930kg. This was just 3kg off breaking his national record.
He wasn't happy that he missed the 343kg lift but he looked at the bright side of an impressive day's work.
"I have to take the positives out of it. I should have had the last two deadlifts, my first issue was with my hand grip and I was gassed by the last one," he said.
"But I'll take the good things out of the comp. I was happy with my squat and the bench."
Whittaker took up powerlifting back in 2012 after suffering a calf injury which scuppered his rugby dreams.
"I had to stop playing rugby because of it. I had blown my right calf five or six times and so I decided to give it away," he said.
"I started hitting the gym afterwards to drop a little weight and spotted a little poster about giving powerlifting a go.
"Right from the first session I was hooked."
Whittaker puts in 20 hours of training and the closer he gets to a competition the heavier the weight he lifts. His training includes a three-hour squat session where he will do exactly that - squat for three hours.
This allows him to come into competitions well prepared and sets him up to get into the right head space for his lifts.
"I have my process. If I run my process I will hit the weight I'm targeting," he said.
"If I don't hit it, it's either a technical thing or I just wasn't strong enough on the day.
"I'm very blank when I lift. I don't see or hear the crowd. It's only when I look back at the video I think 'damn, that crowd was loud'."
Whittaker has his sights on his last competition for the year - the New Zealand Record Breakers in October.
Then all focus will shift to the biggest competition of his life.
"Next year is all about the World Powerlifting Championships in June. It will be my first time there which is exciting."