The Rule Change

The NBA eliminated the illegal defense rules that had mandated man-to-man coverage since 1947. Teams could now play any zone formation — 2-3, 3-2, matchup zone — without restriction.

Statistical Impact

Counterintuitively, the league also introduced defensive three-second violations and anti-hand-checking rules alongside zone legalization, which collectively pushed offense more toward the perimeter. Zone defenses paradoxically incentivized three-point shooting as the counter.

3-Year Average: Before vs. After

The Rule Change

Introduced alongside zone defense legalization, the defensive three-second rule prevented any defender from camping in the paint for more than three consecutive seconds without actively guarding an opponent. This was a concession to offset the impact of newly legal zone defenses.

Statistical Impact

Prevented teams from parking a rim protector in the lane full-time, preserving driving lanes for perimeter players. The rule was a deliberate counterbalance — the league wanted to allow zones but not at the cost of completely clogging the paint. It effectively ensured that zone defenses would be more spread out than traditional college zones.

3-Year Average: Before vs. After