A trailing team removes its goaltender late in a game to add a skater. The decision looks reckless and is in fact a straightforward expected-value calculation.
What the extra skater buys
Six attackers against five defenders creates the same numerical advantage as a power play, and scoring rates with the extra man are substantially higher than at even strength.
The advantage comes from the defence being unable to cover every passing option, so the puck can be moved until an unmarked shooter appears.
Against a team that has been defending for a long stretch, the extra man also compounds fatigue, because tired players cannot chase the puck around the zone.
What it costs
An empty net means any cleared puck that reaches it scores, so the trailing team's risk of conceding rises sharply for as long as the goaltender is off.
That cost is smaller than it appears, however, because a team already losing gains nothing from avoiding a second conceded goal.
The difference between losing by one and losing by two is nothing in the standings, which is what makes the trade favourable rather than reckless.
Why coaches pull earlier than they used to
Analysis of scoring rates showed that the break-even point sits well before the final minute, and that waiting costs more chances than the empty net risks.
Coaches were slow to act on this because a conceded empty-net goal is highly visible and attracts criticism, while a missed opportunity to equalise is invisible.
The practice has shifted gradually, and pulling the goaltender with a couple of minutes remaining is now unremarkable where it once seemed desperate.
The situations that change the answer
A two-goal deficit justifies pulling much earlier, since two goals require far more time and the empty-net risk is proportionally less relevant.
Being on a power play at the same time creates a two-man advantage, which is the strongest configuration available and is used whenever the timing allows.
Conversely, a team defending its own zone cannot change safely, so the goaltender often stays until a stoppage or a clearance creates the opportunity.
How the defending team responds
The leading side stops trying to build attacks and simply clears the puck, since possession in its own zone is worth less than distance from its own goal.
Players position themselves in shooting lanes rather than pressing the puck carrier, accepting that the aim is to survive the sequence rather than to win it.
Faceoffs become disproportionately important, because winning one and clearing immediately can consume a meaningful fraction of the remaining time.
