Your transition defence starts before the shot goes up

Most fast breaks are conceded by a decision about the offensive glass, taken a second before the ball is released.

Nobody loses a break at half court. By the time the ball crosses the timeline the outcome is basically set, and the players sprinting back are just performing effort for the benefit of the bench. The decision was made earlier, when two or three offensive players committed to the rebound and nobody was assigned to the safety position.

Coaches know this. They still get it wrong, because the offensive rebound is visible and the break you conceded four seconds later looks like somebody else's fault. Crash with three and you will win extra possessions. You will also give up layups, and layups are worth more than the second-chance mid-range you gained.

The maths here is not subtle. An offensive rebound converts at something well short of certainty and often produces a rushed putback. A defence that is outnumbered in transition concedes at a rate close to the best shot in basketball. So the trade only pays if your rebounding edge is large and the opponent's outlet passing is poor. Against a team with a big who can throw a two-handed overhead pass to half court, it almost never pays.

I would argue the single most useful piece of transition defence is a guard who reads the shot rather than the rebound. He turns and retreats while the ball is still in the air, on the basis of where the shot came from and how it left the hand. That is an unnatural instinct. Every young player wants to watch the ball.

There is a subtler cost too. A team that crashes hard develops habits it cannot switch off, and habits do not respect game state. You see it late in close games, when the correct decision is obviously to protect the lead and two players still go to the glass because that is what they have done for eighty minutes.

The fix I like is to make the safety assignment positional rather than personal. Whoever is furthest from the rim when the shot goes up retreats, regardless of who they are. It removes the negotiation. It also stops your best rebounder from being the one permanently excused.

Ask any coach what their transition defence looks like and they will describe how they build the wall. Ask instead how many bodies they send to the offensive glass. That answer tells you more.