Nearly every Premier League club now employs someone whose main responsibility is dead-ball situations. The role spread quickly because the underlying argument is unusually easy to verify.
Set pieces are the only rehearsable phase
Open play is continuous and reactive, so a coach can train principles but cannot script the sequence of events that will actually occur.
A corner or a free kick starts from a stationary ball in a known position, with both teams organised and the clock paused.
That makes it the one moment in football where a rehearsed routine can be executed as designed, which is why the coaching return is so much higher.
The margins are large relative to the effort
A meaningful share of goals arrive from dead-ball situations, and the proportion rises in tight matches where open play is congested.
Improving that phase requires training time measured in minutes per week rather than the months needed to change a pressing structure.
For a club with limited sessions between fixtures, it is the cheapest available source of improvement. A team that gains one extra goal from corners across a season has converted a few hours of training into a league position.
Defending them is a separate discipline
Marking schemes involve trade-offs between zonal and man-oriented approaches, and the choice interacts with squad height, aerial ability and the opponent's routine.
Specialists study opposition patterns in detail, since routines repeat and the delivery zones a team favours are identifiable from previous matches.
Defensive set-piece work rarely produces visible highlights, which is why the attacking side of the role receives most of the attention. A goal prevented leaves no trace in a highlights package, though it counts identically in the table.
Throw-ins entered the same category
Long throws returned as a deliberate tactic once clubs began treating restarts systematically rather than as an interruption to be resumed quickly.
Throw-in coaching also covers retention in less dangerous areas, where possession is lost more often than most teams realise.
The principle is identical. A stopped ball is a rehearsable situation, and rehearsable situations reward specialisation more than any amount of general coaching does.
Free kicks in wide areas fall into the same bracket, and the delivery patterns clubs use from them are now designed rather than left to whoever picks the ball up.
Why the advantage may not last
Once every club employs a specialist, the differential narrows, and the phase becomes another area where teams are broadly matched.
Innovations spread quickly because routines are recorded and analysed by every opponent within days of first appearing.
What remains is a permanently higher baseline, which is the usual outcome when an unexploited area of a sport is finally taken seriously.