Back when Kendrick Lamar was only a teenager, he was given a shot by Def Jam to put forth his musical talents.  Even though he must have been skilled back then considering that he was being looked at by Def Jam to begin with, Kendrick claims that at that age he simply wasn't ready.  He spoke about his experience with Devi Dev of MTV's Hip Hop POV of going to a meeting with Def Jam and meeting Jay-Z.

"I don't think even Jay remember that. This was when I was like first turned 17.  And I remember coming out here for a meeting and I was too excited man. And all I remember was Jay walking in the room, 'Yo, what's up?' And walked back to the elevator and we was like 'Damn, that's Jay.' So he doubles back, goes back to his office next door and he's playing my music. Put me in the studio and that was just one of those situations where I wasn't ready."

Source: hiphopdx.com