Anticipation beats instruction
Basketball actions happen faster than they can be called. A cut only works if the passer expects it before it is visible, and a defensive switch only works if both players commit at the same instant. Those are learned reflexes, not tactical instructions, and they are earned through repetition with the same teammates. That is why a group of five players who have played hundreds of possessions together can outperform a nominally more talented group still working out who does what.
Why roster size raises the stakes
With a compact roster, there is limited scope to rebuild a broken combination in-season. A team cannot simply cycle through alternative pairings until something clicks, because there are fewer alternatives available. That makes the initial construction of the starting group unusually consequential and makes any disruption to it expensive. Coaches in this environment tend to protect what works rather than chase marginal upgrades.
The hidden cost of stability
Continuity has a downside worth naming: a familiar group can paper over a structural weakness for a long time, because its execution is good enough to survive a flawed plan. The weakness then reappears in the postseason, when opponents have time to prepare specifically for it. The best-run teams treat stability as a platform for adjustment, not as a reason to avoid it.