The 22-year-old's disappointing London showing, where he failed to lead Australia to the 4x100m relay title and finished second in the individual event, was followed by a lengthy post-mortem back home.
Magnussen was hit with a fine and suspended ban for using a sedative in a pre-Games bonding ritual with team mates and has made several media appearances this year apologising for his role in what was portrayed as a dysfunctional Australian team.
At the Australian championships in Adelaide this week, however, Magnussen put all that behind him and proved that he still has no domestic match over one or two lengths of the pool.
On Tuesday, he won the 100 metres freestyle for a third successive national title in 47.53 seconds - the fastest time of the year in the blue riband sprint.
On Thursday, he again blew away all competition to claim victory in the shorter sprint in 21.52 seconds - his personal best over 50 metres and quick enough to have secured silver in the event at last year's Olympics.
"I got in the warm-up pool and thought 'it is going to be quick tonight'," Magnussen told reporters.
"That was the best 50m I have ever put together technically. The moment I broke out of the water I knew I had it in the bag."
Magnussen will defend his 100 freestyle world title in Barcelona in August and although keen to retain the title he won in Shanghai two years ago, his focus remains on Olympic redemption in Brazil in 2016.
"I think I still have a bit of work to do to get my confidence back up to the level it was leading into the Olympics," he said after his 100m victory in Adelaide.
"But as far as I'm concerned ... we have four years to get my confidence back. While this world championship is really important to me and I'm defending my world title, I want to be an Olympic gold medallist."
- Sports & Recreation