On October 31, 2015, Ayres was selected by the Idaho Stampede with the first overall pick in the 2015 NBA Development League Draft. On November 13, he made his debut with Idaho in a 110–106 loss to the Rio Grande Valley Vipers, recording 18 points, 9 rebounds, 4 assists, 1 block and one steal in 39 minutes of action. On January 29, 2016, he was named in the West All-Star team for the 2016 NBA D-League All-Star Game.
