J. Cole is currently training his ass off in hopes of getting a shot to make an NBA roster ... so says Master P, who offered the rap star some pretty sound advice.

First, let's talk J. Cole -- the "No Role Models" rapper was a solid hooper back in high school and famously tried out for St. Johns during his stint in college, but ultimately decided to focus on music.

Cole is a regular on the celebrity basketball circuit and is widely known as one of the best non-pro celebrity ballers in the country.