"It was by far the most unsuccessful year I've ever had," said Australia's top triathlete.

A former junior world champion with multiple international successes, the 26-year-old Tasmanian was hotly-fancied for both triathlon events at the Tokyo Olympics.

However, a frustrating dearth of international racing opportunities plus a series of niggling injuries contributed to a 16^th place finish in the individual race and ninth in the mixed relay.

"There's a lot of things that went into play for that to be the case. Being stuck in Australia and not able to race at all certainly didn't help," he said.

"It's easy to look back in hindsight and say what you'd do differently but given the same scenario I'd definitely head off overseas earlier to get some more racing in because basically I lined up in Tokyo having only done one race in two years.

"There were races on but being in Australia just made it harder to get there. That was really hard not having any races. I felt that especially as the year went on. There was never a point where I was actually able to get to the top level again."

Now back training in Launceston, the former Riverside Primary, Riverside High and Launceston College student said ideally his pre-Games training block needed to be back-ended by some racing.

"I was going there knowing I was in good swim and bike form but knowing I was just going to have to rely on talent in the run, which obviously is not going to cut it.

"When I left Tokyo and reflected on it I couldn't really expect to be on a podium with what I'd done."

After the dramas of a false start, restart and broken nose in the individual event, Australia's unexpected low finish in the mixed team relay exposed the nation's poor preparation.

Birtwhistle, whose anchor-leg heroics had helped deliver four consecutive world championship medals from 2016 to '19, said it had led to much soul-searching in the months since the Games.

"I think it's the first relay I've ever done where we weren't on the podium.

"Usually there's so much pressure on me as the last athlete to go but by the time I had done my warm-ups and started paying attention to the race I was shocked at how we were going so poorly. By that point it was almost like a fun event.

"The Kiwis were even further back and there was a Canadian I'm good friends with as we were waiting for our teams to come in we were just joking around with each other. What else can you do? We were so far down I even thought we wouldn't get to finish.

"In the end I was really happy with my leg, I think it was one of the quickest. And considering I was not fighting for a medal like the others were it showed me that at least I did well. It was a really strange day. And the next day too, being around everyone having had so much success in the relay before.

"We weren't exactly favourites, but were definitely a pick for a medal and then to finish a fair way off the podium ..."

Returning home after lengthy travels and two weeks' quarantine, Birtwhistle has been back at his favourite training sites and was back in action at the Beauty Point Triathlon on Saturday.

He expects to head to the Gold Coast in January to team up with his coach Joel Filliol, who was appointed Triathlon Australia's podium centre head coach in January.

Overseas competition should resume in May with a focus on adding to his two 2019 wins in the World Triathlon Series. Although two rounds have already been held - in Hamburg and Abu Dhabi - Birtwhistle expects to compete in the remaining five beginning in the Japanese city of Yokohama, on May 14-15 and also including Leeds, Montreal, Hamburg, Chengdu and then back to Abu Dhabi for the series finale.

He will also be looking to build on 2018 gold and silver medals from the Gold Coast when the Commonwealth Games are held in Birmingham, England, from July 28 before his thoughts return to the Olympics.

"For a number of reasons Tokyo wasn't the Olympics I expected and worked for, both in terms of performance and the environment because of the way everything was," he said.

"So I'm pretty motivated now to work towards Paris (in 2024) and by then things will be a bit more straightforward and normal.

"In an ideal world, I would have wanted to get the experience in Rio and then go to Tokyo as a favourite.

"Instead I was going as an outside favourite without the experience, whereas now I've got that and Paris isn't far away.

"I will go into 2022 as normal. I don't feel like I'm playing catch-up any more.

"It was a disappointing year results-wise but I'm over it and able to get on with the next year."