J. Cole Seriously Training for NBA Career, Says Master P

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.

The 35-year-old recently hooked up with Master P for a Puma commercial where it's strongly insinuated that Cole is training for a shot with an NBA team ... which makes sense since P basically did the same thing back in the day.

Master P says he earned an NBA contract with 2 different teams in the '90s -- after he was already a famous rap mogul -- and he knows what it takes to get to the top level.

P -- whose music and hoops careers are documented in BET's "No Limit Chronicles" -- tells TMZ Sports he had a lengthy conversation with J. Cole about his hoop dreams ... and says he's convinced the rapper is dead serious.

"When I talked to J. Cole, he was like 'You know, big dog you did it. What do you think I would have to do to make it happen?'"

"I said to get one of these NBA jerseys, it's not gonna be easy. It's gonna be a lot of hate, it's gonna be a lot of people not believing in you but you know J. Cole -- he got the right size, he in the gym!"

"But, what I told him ... this a different time we're in. They're going to pick you apart! You're gonna have to be able to hit every shot and if you don't hit every shot, they -- you know in the NBA, they don't hit every shot but they believe in them. So, you're gonna have to go somewhere where the team really believe in you and the players believe in you."

P says Cole won't get a pass just because he's famous -- in fact, he'll have to work even harder than everyone else to prove he's for real.

"They've been putting their whole life into this. So, you're gonna have to prove you're worthy of being on that court."

P adds, "I believe in him and I believe that he's a youngster that has a lot of desire."

Bottom line -- P says if Cole does get an opportunity, he's gonna have to show out.

"Either you're gonna be good enough to play or you're gonna get exposed."