John Legend thinks Kelsea Ballerini has been "very good" on 'The Voice'.

The 31-year-old singer debuted as a coach on the hit TV show in February, and John has been impressed by his co-star, observing that she's been a "wonderful" addition to the line-up.

John, 46 - who serves as one of the coaches alongside Kelsea, Michael Buble and Adam Levine - told 'Extra': "She took to the show quickly.

"She's been a guest on the show before; she guest coached for Kelly [Clarkson] before and so I think she came in just knowing how everything worked and she was ready to go.

"She has such a great personality. She's been very good at winning artists for her team, especially the ladies. I definitely knew I had no chance against her with some of the ladies. You could tell the girl power thing was working.

"She's been wonderful and she's been great to get to know on the show."

John has also relished the experience of competing against Adam.

The 46-year-old star returned to 'The Voice' earlier this year, having previously appeared on the show between 2011 and 2019, and John has been impressed by his co-star.

He said: "I was hoping he was a little rusty and wouldn't know what to do, like I had to explain a few things. No chance. He was ready and he's probably been my stiffest competition when it came to four-chair turns and getting the artist that we both wanted.

"He was definitely my stiffest competition when it came to that, so my favorite moment of the year so far was when I blocked Adam for Renzo, and it's causing pain every time Renzo's performing because he loves him so much and every time he performs I just look over there like, 'Yeah, I blocked you.'"

Adam previously explained why he decided to return to 'The Voice'.

The singer told E! News: "I was ready to do it, then the stars aligned and here I am."

Asked if he ever had any regrets about quitting 'The Voice', Adam replied: "It's funny, I actually didn't miss it while I was gone. But I became more nostalgic about it once I came back."