Cody Simpson has missed out on a spot on the Australian swimming team for the FINA World Championships.

The pop singer’s rollercoaster week ended with a deflating moment when he finished last in the final of the men’s 100m freestyle on Saturday night in Adelaide.

Simpson had a whirlwind day after initially being disqualified for the final for a false start during the heats on Saturday morning.

The 25-year-old jumped the starting gun, however, he was successful in protesting the disqualification.

He was reinstated just hours before the event was held on Saturday night, and raced from lane eight after qualifying for the final as the equal-seventh fastest qualifier.

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Simpson will be thrilled to have swum a personal best time of 49.34, but he also learned how far he has to go in the 100m freestyle.

In a race that didn’t include 100m freestyle king Kyle Chalmers, Cameron McEvoy and Alexander Graham, a new star emerged with William Yang being crowned the national champion.

Yang finished ahead of Zac Incerti and Flynn Southam in a time of 48.55.

Simpson needed to finish in the top six to keep his slim hopes of a spot on the 100m freestyle relay team alive.

His personal best of 49.34 was just 0.22 seconds away from a top six finish.

The time smashed Simpson’s previous best time in the event by more than a second.

Freestyle is not his preferred stroke, but the Queenslander proved he can challenge the country’s best in the pool despite only returning to the sport in 2020.

Simpson may have missed out on the world championships in Budapest, but his spot on the team for the Birmingham Commonwealth Games is expected to be confirmed on Sunday.

He earned his spot at the Commonwealth Games, beginning on July 28, after finishing third in the men’s 100m butterfly final on Thursday evening.

His dream of swimming at the world championships was dashed when Chalmers’ suddenly backflipped on a previous decision to skip the event.

Speaking to reporters on Thursday, Olympic champion Chalmers explained that he would make a final decision on whether to compete in the event after consulting his coach in the next couple of days.

Because Chalmers finished second in the 100m butterfly, Simpson would miss out on a ticket to Budapest if the South Australian chooses to compete at the world championships.

On Friday, Chalmers reached out to Simpson to clear the air as rumours swirled about their relationship since it was revealed that the pop singer was dating Olympic icon Emma McKeon.

Chalmers and McKeon previously dated, with their relationship first becoming public knowledge in September.

“We had a chat last night,” Simpson told Amazon Prime Video.

“He was cool, he sort of reached out and we sort of cleared the air about it. So it’s all good in that sense. I would sort of respect his decision either way.

“I sort of realised he’d changed his mind as he has every right to do obviously.

“He has the spot. I didn’t finish second, I finished third. So for him to have done that (finished second) especially with the limited prep he has had is pretty remarkable.”

Simpson said he was just thrilled to part of the emerging blockbuster butterfly rivalry between himself, Chalmers and Matt Temple.

“It’s exciting to be a part of something like that,” he said.

“To have been one of those three guys for me is crazy already. I look at those two guys and even up until two days ago I thought, ‘God, they are so far ahead of me. I have so much work to do to even be in the running’.”