Jefferson was selected with the final pick in the 2014 NBA draft by the San Antonio Spurs On 26 June 2014. He was later traded to the Brooklyn Nets on draft night. In July 2014, he joined the Nets for the 2014 NBA Summer League.On July 23, 2014, he signed with the Nets.On January 1, 2015, using the flexible assignment rule, the Nets assigned Jefferson to the Maine Red Claws, the affiliate of the Boston Celtics.On 08 January 2015, he was recalled by the Nets.