Kemp was rushed, forget his age, look at his career PA. 548 college, 1315 minors.
He needs another 1/2 season in AAA ball.
Which is why they're doing the right thing with Crawford.
There's a few uber talents that can skip development and learn on the job, but most players need close to 2500 PA to be ML ready. Which is why most college players start their careers in low A, college replaces rookie league time and some low A experience.
Kemp signed at 22 but barely played, A/A+ at 23, A+/AA at 24, AAA/PHL at 25.
Crawford only has 1386 PA. He's still only 21. There's is no reason to rush him.