Usain Bolt beaten
The triple gold medallist from both the 2008 Beijing and 2012 London Olympics easily won his heat in 46.71 seconds at the Camperdown Classic.
But he had to settle for third place overall after his training partners Warren Weir and Yohan Blake both posted faster times in their heats.
"I'm happy, I've never been so nervous running a 400m but overall I'm happy. Physically I felt good, not as good as I normally would, but overall I feel good," Bolt .
"I didn't matter about the time, I just wanted to complete this race, I know I may have one more for the season, maybe two depending on what the coach wants."
Weir, who finished third behind Bolt and Blake in the 200m final at London last year, won in a personal best time of 46.21 seconds.
Blake, racing in the same heat as Weir, stopped the clock at 46.64 after fading in the final straight following a blistering start.
"I feel strong, I tested myself in the first part of the race, that is what got the better of me in the home straight, but I'm feeling pretty good," said Blake, who won the 100m world championship in 2011 when Bolt was disqualified for a false start.
"Training is going really... you know, I'm confident, I have the world championships to defend my title and coach (Glen) Mills is just working on the different parts of my race and I'm feeling good."
The places were decided by heat times because there was no final for the event, which was part of a meeting run by the Racers Track Club that attracted around 30 athletes.
Bolt is the world record holder and double Olympic champion for the 100 and 200 sprints but often competes in 400 races at the start of each season to build his fitness.
His major goal this year is the world championships in Moscow.
"It was about getting through the first one, so I can be more confident for the others," Bolt said.
"I'm just very happy that I am fit at this time of the season to be able to compete in this race.
"Training has been going very well, I haven't had any problems and that's a good sign so I'm just working hard."