The bare facts of Sullivan's year are this: During his end-of-season break, Sullivan contested the Coast to Coast endurance event. Following the trials to choose the elite crews for this year's European campaign, Cohen was left out of the first World Cup regatta in Sydney in March. He had been off the pace while recovering from the endurance race.
He was then chosen for the single seat for the next two cups in Eton Dorney in June and Lucerne a month later - filling Olympic gold medallist Mahe Drysdale's role while he took time a break.
It didn't work, to put it mildly, and Sullivan pulled out of the world champs in South Korea in August and - although it sounds rather dramatic - that might have been the end of the career of one of the country's finest sportsmen.
Sullivan puts the problems around the time off and Coast to Coast down to a lack of communication between Rowing New Zealand and himself on when he was required back on the water.
"The timing didn't really fit too well and it went pear-shaped from there. The recovery period is quite large because you destroy everything.
"I was quite down and wasn't really on form from doing the Coast to Coast. But I don't regret doing that. It was always something I'd wanted to do and I was pretty stoked I managed to knock it off and finish it."
The result was that while he was not unfit, he wasn't "where I should have been".
"Just being that little bit behind is quite mentally draining going up and down the course, so I wasn't in the best space".
Crews were being finalised and there was no room, even for a reigning Olympic, and multi-world champion athlete.
Sullivan had twice won the world under-23 single scull crown so filling Drysdale's shoes, even on a temporary basis, shouldn't have been a problem, right? Wrong.
" I didn't really have the passion to be in that boat. You've got to be really focused to be going fast in the single and the whole time I was probably more regretting doing it than anything.
"I had a lot of back and forth. I probably was even slightly depressed about the whole situation and I wasn't enjoying rowing at that point. I looked at finishing."
What kept Sullivan going was talks with a range of people. He singles out the highly respected Don Rowlands as providing inspiration, and even some rivals.
"They said 'what the hell are you worried about, you're an Olympic champion and a year off is not going to hurt you'. That brought it home to me, I had focused so much on not being in the team, not being where I should be, and I was probably getting a bit down on myself."
Sullivan faced a dilemma elite athletes would recognise; what to do once you've climbed your Everest?
"I'd spent my whole 12 years of rowing focused on winning an Olympic gold, that was really the only thing I wanted to do.
"Having got to the point of having achieved that it was 'why do I want to do it again?' It was a risk, trying again and failing.
"There were a lot of things running through my head and reassessing goals is a hard thing to get around once you've been so focused solely on one thing."
After deciding to skip the worlds, and taking a few weeks break, he turned to High Performance Sport performance physiologist Daniel Plews and worked out a training programme with more variety in it to get his base fitness back up.
That helped reignite the passion and now he's part of the summer training group working out in double and quad boats, and loving it.
Sullivan is clearly someone who likes competing and training with others. He's finding sitting in a quad with younger guys is highly motivating - "they push me along". He is working on being the fittest he can be going into the Christmas break.
"I want to put myself in the best situation come the trials (early next year) and try for the boat that's going to have the most chance of medalling," he said, adding he has a high regard for the potential within the quad.
Reuniting with Cohen - who is recovering from an episode of irregular heart beat which forced him out of the quad during the worlds - for Rio? Sullivan says he's often pictured it, but much has to happen first. It's a tough game and just getting a seat will be challenging.
"I'm pretty positive I can get myself into the best position to give it a good nudge again."
Sullivan will look back on the last year as a valuable learning experience. "I guess if I could do it all again I would do it a bit differently. I learnt a lot from it so it's probably given me a lot more skills for the future."
