We see "excellent" defenses; what made them effective? There is no "secret sauce." Players combine awareness, alertness, effort, and technique to bake execution (SKILL AND WILL).
We need the personnel, strategy, and operations to execute.
Account for pace. Points per 100 possessions does that. A slowdown team will allow fewer points solely because of pace. Break down how many came on free throws, transition, threes, layups, offensive rebounds, et cetera. If we want to be better, correct weakness like poor closeouts, bad fouls, and poor rebounding.
Master individual technique. Gregg Popovich remarks, "technique beats tactics." It demands playing from a stance, good position, interior and perimeter technique, multiple efforts, ball pressure, effective closeouts, contesting shots without fouling, and solid defensive rebounding.
Get everyone on the same page with CORE VALUES. Starting players didn't know the team offense or defense. The coach explained there would be a test and players who didn't pass wouldn't start. Guess what? They learned. Create higher expectations. There's literally only one rocket scientist in my house (my wife).
"Know your NOs."
Attitude. Get your head right. "Attitude reflects leadership." Defensive mindset instills controlled aggression.
Attack the ball. Defensive excellence begins with ball pressure. Have no fear. "Play the coverage and trust the protection."
Reverse engineer success. Brian Robb discusses the Celtics' defense at BostonSportsJournal.com. "Special things are happening already. The Celtics have the third-best field goal defense and the top 3-point defense in the league. They rank sixth in defensive rebounding. They don’t send opponents to the free-throw line at a high clip (third-fewest attempts allowed in NBA). There just aren’t any glaring weaknesses in either of these groups, whether it’s the starters or second unit out there."