ESPN's Adrian Wojnarowski first reported the news.
Vanderbilt averaged 5.9 points and 7.9 rebounds during his lone season at Kentucky. He shot just 42.6 percent from the floor and was consistently a minus on the offensive end.
"Being a professional basketball player has always been a dream of mine," Vanderbilt said (h/t Jon Hale of the Courier-Journal). "From the moment I first picked up a basketball when I was four years old, I knew it was something I wanted to do for the rest of my life. These past couple of weeks have been extremely difficult for me. With everything I went through this past season, I've had a lot to think about and what's best for me and my future. Through it all, I've become a better man on and off the court.
"First off, I want to thank God for blessing me with this opportunity because without Him, none of this would be possible. I also want to thank all of the people in my life who have supported me throughout this entire process—from my family, to my teammates, to the coaches and UK staff, and most importantly the fans. The relationships I've built here will last a lifetime and I will cherish the memories I've made here forever.
"After going through the process, I was able to get some positive feedback that confirmed what I had hoped: that my time is now. It is going to be tough to leave this place, but I've decided to remain in the NBA draft and pursue my dreams now."
Vanderbilt is considered by most as a mid-second round choice. He showed little offensive game to speak of but has major potential on the defensive end. His length allows him to block and alter shots near the rim, and he's an elite athlete who could become a roll threat on pick-and-rolls.
There's a clear lack of polish to his game; he's a ball of energy and athleticism that hasn't come close to putting it all together.
That's why there was a clear expectation he would return to Kentucky, polish his game and potentially lock himself into the top 20 a year from now. It seems the allure of the NBA was too much to pass up.