Leading the Rabbitohs to the finals in his first year at the top job, he was offered a lucrative five-year deal to join the Broncos which turned into a disaster.
Taking the deal he regrets making the "business decision" which set him back in the coaching ranks.
"I made a business decision in the end. Ultimately, it proved to be the wrong decision," Seibold said.
"I do regret it. It was a five-year deal with the sixth year in my favour. Very lucrative."
"I said 'no' a couple of times but then another year kept getting added, and it got to the point where I felt as though if I didn't take it, it's probably negligent in some way."
Announced as the new Broncos coach in 2018, he took over from coaching immortal Wayne Bennett in 2019. From the get-go, the writing was in the stars as they endured their equally worst start to the season, only winning two of their first eight games.
Only just making the finals in the eighth spot, they suffered their worst finals defeat losing 58-0 to the Parramatta Eels.
"It was just the way we bowed out; we got beaten 58-0 in the finals. It was just horrible."
"We beat that Parramatta side 17-16 two weeks earlier. So, do you lose your talent in two weeks? Do you lose your fitness or your contact ability in two weeks? You don't."
"I didn't see it coming."
The next season was even worse. After recording the worst year in Brisbane history, and claiming their first-ever wooden spoon he was terminated from his contract.
He left the club as the only coach in Broncos' history not to have a winning record. It was even reported during the 2020 season, Seibold was offered $1 million to leave the club
"I regret it heaps, but then maybe I wouldn't be the coach I am today if I didn't go through that experience of so much media exposure (that came with) going to Brisbane."
"Looking back now, it seems a little bit surreal. It seems like a lifetime ago, even though it was only a couple of years ago."
"But I feel like I'm a better coach and even a better person. It was tough at the time, and I can see why people criticised me externally, but that's life and you get on with it."
Since then, Seibold has gone on to be an assistant coach at the Newcastle Knights and work as a defence coach for the England national rugby union team. Now back in the NRL, Seibold will be hoping he won't have a similar experience to that at Brisbane.