Basketball's three-point line changed the sport more than any other rule of the modern era. The effect was not simply more long shots but a wholesale rearrangement of where players stand.
The arithmetic favoured the longer shot
A shot from beyond the arc is worth half as much again as one inside it, so a lower success rate can still produce more points per attempt.
Once teams measured this properly, the mid-range shot became difficult to justify, since it carries similar difficulty to a three without the extra reward.
Shot selection shifted towards attempts at the rim and attempts beyond the arc, and the space between them emptied out.
Defences had to stretch outward
A defence that ignores shooters beyond the arc concedes the most efficient shot available, so defenders must contest the perimeter.
Pulling defenders outward removes them from the area near the basket, which is precisely where they were previously most useful.
The interior therefore opens, and a driving player faces fewer bodies between the perimeter and the rim than in earlier eras.
Spacing became a coached quantity
Offences now position players at deliberate intervals around the arc so that any defensive rotation leaves someone open.
The intervals matter because a defender can only cover a limited distance in the time a pass takes, and spacing is calibrated against that.
Movement patterns are designed to preserve the spacing rather than to disturb it, which is why modern offences can look static before the ball moves.
Player roles changed as a consequence
Tall players who once operated exclusively near the basket are now expected to shoot from distance, because a non-shooter allows a defender to sit in the lane.
Guards are asked to shoot from further out than the line requires, since a longer range stretches the defence further still.
Players unable to shoot from range have become harder to accommodate, regardless of their other qualities, because their presence costs the team space.
The counter is length and switching
Defences responded by fielding players who can guard multiple positions, allowing them to switch assignments without conceding a mismatch.
Switching removes the screening advantage that creates open perimeter shots, at the cost of occasionally leaving a smaller player defending near the basket.
The resulting contest is between offences trying to force a mismatch and defences trying to survive without one, which is a different sport from the one the rule was introduced into.
