Natalie Gauci auditions for fellow Idol winner Guy Sebastian on The Voice

Guy Sebastian couldn’t quite place where he knew this fellow Idol winner from - before telling her she “hadn’t nailed” her Voice audition.

The Voice coach Guy Sebastian found himself in an unusual position in Tuesday night’s episode when a fellow Australian Idol winner fronted up to the blind auditions.

And in a slightly awkward exchange, Sebastian at first appeared unable to place how he recognised her, before telling her she “hadn’t nailed” her performance.

Sebastian won the first season of Australian Idol in 2003, while Natalie Gauci’s win came four seasons later, in 2007. There have been seven Australian Idol winners, with Casey Donovan, Kate DeAraugo, Damien Leith, Wes Carr and Stan Walker joining Sebastian and Gauci in the winners’ circle.

Guy couldn’t quite place where he knew Natalie from at first.

It’s a small club, but Sebastian failed to recognise where he knew Gauci from after her soaring performance of Sia’s hit The Greatest.

After Sebastian and Delta Goodrem had turned their chairs for her, the singer at first introduced herself as simply “Natalie”.

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“I know I’m looking at you weird, but do I know you? Can you tell us a bit about yourself?” he asked.

“Uh, well, OK. My name is Natalie Gauci, and you might know me from another TV show called Australian Idol?” she asked.

Gauci said she was surprised to be back on a reality show.

She told Guy after winning Idol her personal life had “gone a little bit downhill”. Earlier, she’d admitted she was surprised to have taken up the offer to appear on The Voice. “I can’t believe I’m back on a reality music show … I cannot believe it.”

Despite turning his chair, Sebastian offered some tough critique amid the praise.

“You’ll watch this back and think, ‘I didn’t love that bit.’ There was bits where I thought, ‘She hasn’t nailed that.’ But in the end, what I heard was vulnerability. As a coach, I’d love to help you rediscover why you fell in love with singing in the first place,” he said.

The pair got a happy ending, with Gauci choosing Sebastian as her mentor on the show.

Sebastian is undoubtedly Australian Idol’s biggest success story, having sold more than 4.7 million albums and singles in Australia across a prolific 17-year career.

Gauci’s Voice journey will continue – with Guy as her mentor.

Gauci’s career path is perhaps the more common Idol winner experience: A hit single and high-charting album in the weeks after her season ended before fading from the spotlight.

Gauci reflected on her rocky post-Idol journey in a 2017 interview with news.com.au.

“Instead of going with the flow, with the ‘machine’, I resisted it and became more rebellious in terms of my attitude and my musical choices. That’s what artists do, but if you’re from Australian Idol, then maybe it’s not a good fit,” she said at the time.

“I was naive about the music industry. I wasn’t sure how it all worked and I wasn’t thinking about the business side of things. I went into a bit of depression, and by the time my record company and I came to a mutual agreement, I was too far gone. I walked away just knowing that I wanted to do things differently.”