Mack Horton, the Rio Olympic 400m freestyle champion, did not make the Australian swim team for Tokyo in the event.
Horton, a 25-year-old from Melbourne, finished third on the opening night of the Olympic Trials in Adelaide on Saturday. The top two make the team.
Elijah Winnington won in 3:42.65, prevailing by .62 over Jack McLoughlin. Horton, who won the Rio Olympics in 3:41.55, touched in 3:43.92.
In 2016 in Rio, Horton became the first Australian man to win an individual Olympic swimming title since Grant Hackett in the 1500m freestyle at the 2004 Athens Games.