When did he know? When do you think Tupac Amaru Shakur or Lesane Crooks (according to some "documents" of dubious origin) realized he was gonna be one of the greats? Not just a good or passable rapper as this first song shows but a titan. If you played Same Song from Digital Undergrounds This Is An EP Release and said that to me, I would have slapped the looney clean out of you.
Later on that year a month or so after DU dropped Sons Of The P, Tupac (now 2Pac) dropped 2Pacalypse Now. The album came out at a bad time in rap when every politician was scapegoating rap for damn near the cause of hunger in 3rd world countries. Even with Brenda's Got A Baby and Trapped, the album was a dud at the time and we wouldn't get an album from him for two years until Strictly For My N.I.G.G.A.Z. We all know what happened after I Get Around and Keep Ya Head Up came out so it would be redundant to retell it. It's safe to say that average XClan rapping cat stepped his game up and poured his heart into a pen and then put it to paper. He is maybe one of the 10 greatest rappers of all time but you wouldn't guess it by his first display. Then again, Kobe averaged 7.6ppg his first year and he turned out decent.
Although 'Pac only rhymes on one track, it's an important part of the puzzle for 2Pac completists. The album has only two exceptional songs: the Jimi Hendrix sampled The Way We Swing and the very jazzy R&B-esque remix to Sex Packets. If not for it being the world premiere of one of the gods of rap, I'd definitely tell y'all to leave it alone.
Digital Underground-This Is An EP Release