Katy Perry, Lionel Richie and Luke Bryan can learn a thing or two from their rivals Adam, Blake, Alicia and Kelly ... and that's according to an "American Idol" winner!
Nick Fradiani -- who won season 14 in 2015 -- watched the big premiere, and says the "Idol" judges have some work to do if they're gonna build up the same kind of chemistry as "The Voice" coaches.
To be clear, Nick thinks they can do it, but he has a deadline in mind for when it's all gotta come together on camera. As far as this year's contestants hooking up, as we reported, Nick ain't all that shocked ... and he spills some tea.