The Aussie's decision was based in part by Red Bull's decision to race Honda engines with Ricciardo fearing that talk of the Japanese manufacturer's improvements are just that, talk.

However, if it is not, he's also had to make peace with the idea of his former team-mate Verstappen winning the 2019 World title.

"Actually, part of the decision-making for me, I put myself in the mindset of 'What if Honda and Red Bull kill it, and what if Max becomes World Champion?'" Ricciardo told RACER.

"So I had already played that through my head and become OK with it, or come to terms with it.

"I think at the end of the day, the way I saw it was one of the big things that led me back was I just felt like I needed change regardless.

"Even if the team kills it in 2019, I don't know if I would be convinced that I would be getting everything out of it, if that makes sense.

"So I've come to terms with however it's going to play out, and I believe regardless it's the right thing for me."

The 29-year-old touched on his time with Red Bull, which ended with seven race wins, 29 podiums and three pole positions.

What it didn't end with, though, was a genuine title challenge.

"No, I wouldn't say any regrets," he said. "Not at all, actually.

"I guess as well I never really had many other options anyway, so it's not like I could have signed with Mercedes two years ago and I didn't want to or whatever. So no regrets. I'm happy.

"I look at 2018 and 2015; there's been some frustrating years for sure, but I'm always happy with the way I approach it.

"I don't look back and say 'Ah, if I would have worked harder then I wouldn't be in this position and I would have made things better for myself'.

"I don't ever feel like I've cheated myself, and some of my best weekends have been when I've been more chilled about it and less intense.

"But I think I've found that balance, so no regrets."