But in the series finale, he really hit his straps, finishing runner-uo to former 100m world record-holder Asafa Powell over 60m and then Bolt himself over 150m.
The experience proved an eye-opener for the Kiwi's quest to qualify for this year's world championships and next year's Commonwealth Games.
"Since Nitro, to turn up to high level competition and perform as well as I did, I started to realise where I was in my preparation," says Millar.
"It gave me the confidence to see how far I could take it and what was left to do in the season."
Since that awakening, Miller has simply been in white-hot form and will take that streak into this weekend's nationals, hoping only for favourable weather.
Two weeks ago, at the Auckland championships, conditions were too favourable. His 10.11s over 100m would have equaled the national record and edged under necessary qualifying standards, but was negated by over-the-limit tail winds.
Last week, in Canberra, he registered legal PBs over 100m (10.24s) and 200m (20.68s) in less-than-ideal conditions.
"Preparations are going better than I could have anticipated," he says. "I still have the utmost focus on getting those times and if I get one, they should all fall.
"It should have happened the weekend just gone, but the wind wasn't much help. If I can get a little bit of co-operation from the weather and a good crowd, we should see some quick times."
Porritt Stadium looms as a happy hunting ground for Millar, 24, certainly happier than previous years, where venues have not been conducive to running fast.
"It's considered to be one of the best tracks in NZ for fast times and good conditions," says the three-time defending champion over both distances. "In other years, when we've had nationals in Wellington and Dunedin, by the time March rocks around, winter has pretty much set in for a couple of weeks.
"I definitely know that it's in my legs. Over the past few weeks, I've been running faster and faster, but know I haven't reached my max potential.
"There's a feeling when you run faster, but know you can go quicker. You can feel where your body show be when you're 100%, with family and friends watching and national titles up for grabs.
"It should all be there at nationals."
NZherald.co.nz will live-stream the NZ track and field championships on Saturday and Sunday, starting 8am.