The R&B singer made the comments in an interview with The Hollywood Reporter, where he also explained that the Duets judges get on well in spite of occasional on-screen spats.
"I don't think any of us are taking it too personally, because we all actually truly respect each other. Jennifer Nettles, Kelly [Clarkson] and John [Legend], these are great singers," Thicke said.
He continued: "For me, I'm the underdog of the group. I'm just happy to be part of it and give my best I can each week."
Thicke went to say that he's very impressed with the level of talent possessed by his contestants Alexis Foster and Olivia Chisholm.
"When I saw their tapes, I saw these beautiful spirits and I saw this great talent in both of them. And then when I got to sing with them in person, I thought there was a connection," the star explained.
"This show isn't just about them [singing] on their own, it's about how we blend together. So once I realised we can look in each other's eyes and create a spark on stage, that was when I made my decision."
Kelly Clarkson recently revealed that she particularly likes Duets because the contestants are treated with respect.
Duets airs Thursdays at 8/7c on ABC.
Watch Robin Thicke perform with Alexis Foster on Duets below: