United Kingdom, May 13 -- 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 agai...