NBA Cup, the Spurs defeated the Rockets 121-110. Castle continued to play the role of connecting the team in this campaign. He started for 36 minutes and made 5 of 12, 0 of 4 three-pointers, 4 of 5 free throws, 14 points, 6 rebounds, 13 assists (a season high), 2 steals, 1 block, and 5 turnovers. The plus/minus value was +25, the highest in the game!

In the last 5 games, Castle averaged 19.8 points, 5.8 rebounds and 7.6 assists per game.