Country star Kelsea Ballerini has replaced sick Kelly Clarkson on U.S. talent show The Voice.

The Since U Been Gone singer has pulled out of the Battle Rounds of the hit show, and Ballerini was announced as her fill-in on Monday night's episode.

The Voice shared a clip on Instagram ahead of the change, which showed Clarkson making a call to Ballerini, saying: “Hello, thank you so much for doing this for me.”

“Unfortunately, our own Kelly Clarkson was not feeling well this week,” host Carson Daly explained in the clip, adding: “Kelly’s staying at home and she’s watching the battles remotely.”

Ballerini has since made her debut on the panel alongside Blake Shelton, John Legend, and Nick Jonas for a new teaser, telling her shocked fellow judges: "Just pretend I'm Kelly!"

"Who do we blame when you make a mistake?" Legend responded, prompting the newcomer to quip: "Her!"

Ballerini was also quick to carry on Kelly's tradition of poking fun at the other coaches, telling Shelton: "Hey Blake, have I ever told you that you look like my dad?"

The Hole in the Bottle hitmaker has taken to social media to thank Clarkson for the chance to sit in for her, stating: "When she (Clarkson) calls and asks you to keep her seat warm, you put all those years of being her superfan to work... forever #teamkelly."

It's not known if Clarkson's illness will impact her billed performance at Michelle Obama's virtual Girl Talk livestream on Thursday.