The Apaches (3-4) came up short on their game-tying attempt and went scoreless for the final two minutes, thanks in large part to Sevan Zarifian's lock-down defense on Arcadia's Chris Severo.
"Sevan's defense set the tone for us," Stephens said. "He was huge."
Castaneda and Zarifian were instrumental throughout, combining to score all of the team's first-quarter points.
"I believe the hardest defense creates the best offense," said the point guard Zarifian who also had nine points.
The two guided a 13-0 run in the frame to turn a four-point deficit into a nine-point advantage for the Golden Knights (5-4). Castaneda hit two threes on back-to-back possessions for the first six of the 13, with Zarifian taking care of the back end.
While Zarifian's scoring halted in that opening period, Castaneda put in 24 for the game, but none were bigger than the last three.
Ironically, it concluded a second half in which he struggled from the field, scoring eight points — five in a fourth quarter that saw the Apaches hold a lead on two occasions in crunch time.
"I just keep on shooting," said Castaneda. "I'm a shooter and my teammates expect me to shoot."
The guard, who earned all-tournament honors, was also quick to give credit to the defense.
"We just need to continue playing good defense," he added. "Defense wins championships."
As Castaneda cooled down a bit, Severo lit up and hit three from behind the arc — the third giving the Apaches a 49-46 lead and their first since leading, 8-4, in the first.
Severo finished with 21 points in the game, scoring nine in the fourth quarter.
In the end, however, defense prevailed, as Arcadia scored just two points in a little over three minutes down the stretch.
"They were very hot in the fourth quarter," Stephens said. "Sometimes it's hard to respond but we never gave up."