Education
Johnson attended Saint Patrick High School in Elizabeth, New Jersey.
Johnson attended Saint Patrick High School in Elizabeth, New Jersey.
He played college basketball for the University of Kentucky. During the 2010-2011 school year, once coach Kevin Boyle left for Montverde Academy, Johnson followed his coach, where he had to sit out the 2011-2012 season due to the transfer. Because of his excellent grades, Johnson decided to reclassify, thus making the 2012-2013 season his final and senior season at the high school level
He ended up averaging 17.0 points, 11.0 rebounds and 4.3 blocks per game as a senior.
He subsequently earned selection to the 2013 McDonald"s All-American Boys Game and Jordan Brand Classic. Considered a five-star recruit by Entertainment and Sports Programming Network.com, Johnson was ranked as the Number.
2 center in the nation in 2013. As a freshman at Kentucky in 2013-2014, Johnson spent the season backing up teammate Julius Randle and averaged 5.2 points and 3.9 rebounds in 39 games.
As a sophomore the following season, he again played back-up, this time to freshman big man Karl-Anthony Towns and junior Willie Cauley-Stein.
He again appeared in 39 games in 2014-2015 and averaged slightly higher numbers with 6.4 points and 4.6 rebounds per game. On April 9, 2015, Johnson declared for the National Basketball Association draft, forgoing his final two years of college eligibility. He was joined alongside fellow Kentucky teammates in Aaron Harrison, Andrew Harrison, Karl-Anthony Towns, Willie Cauley-Stein, Trey Lyles and Devin Booker.
On June 25, 2015, Johnson was selected by the Oklahoma City Thunder with the 48th overall pick in the 2015 National Basketball Association draft.
He later joined the Thunder for the 2015 National Basketball Association Summer League where he averaged 7.6 points and 8.6 rebounds in five games. On November 3, 2015, he was acquired by the Oklahoma City Blue of the National Basketball Association Development League, the affiliate team of the Thunder.
On November 14, he made his professional debut in a 110–104 loss to the Austin Spurs, recording 16 points, 9 rebounds, one assist, one steal and one block in 33 minutes.