Players get fitter with age. The rest is someone's work.
His signal is the fitness gain above what age alone would give, isolated, attributed to him, and tested across clubs.
Good people at good clubs build athletes, not the building.
Everyone else in the market rates the place: a good sports-science department. But a department is a series of people with different fingerprints. A club that ran three performance leads over twenty years has one blurry average and three distinct individuals underneath it, and the divergence is the whole signal.
The club's one number calls all three eras the same. The truth is that two of these people built athletes and one did not, and to anyone hiring, or any player choosing where to go, that is the only thing that matters. Rating the named person, with the club rated separately on top, keeps what the department average smears away. The place is public. The person is the signal, and the engine separates them.
Illustrative engine read on the real portable-actor structure (the named performance lead rated as a portable fingerprint, distinct from the club's blended developmental value). Composite people and club, demonstration figures.
Subtract what a young body does on its own.
A young player gets faster and stronger anyway, so raw improvement is not the metric. Subtract the maturation-expected curve for the player's age and starting level, and the residual above it, scoped to the physical clusters, is the performance-lead signal, pulled out of the manager's credit so it is never counted twice.
The point is to credit the coaching, not the calendar. A sixteen-year-old adding pace is mostly growing up; the residual is the slice a specific performance lead reliably produces above the growing-up, across many players. It becomes a prior on what the next player will add and how gently his prime declines, because a well-conditioned athlete ages more softly. The gain that outruns maturation has a name attached to it.
Illustrative engine read on the real performance-lead residual (physical-trait development above the age-and-maturation baseline, scoped to Pace & Explosiveness and Strength & Stamina, via the manager credit-split; a projection-and-prior layer, never a KR change). Composite player, demonstration figures.
If it does not reproduce at the next club, it was never his.
A physical residual at one club could be the person or it could be the roster and the facility. The only way to know is portability: does it reproduce when he moves. A residual that holds across clubs is his; one that collapses on a move, especially where the old club keeps building athletes without him, was the place.
Portability is what turns a claim into an asset. Anyone can look good with a physically gifted squad for a season; a performance lead who reproduces his residual across clubs and across borders owns it. Cross-country moves are priced as a confidence shift and a bounded adaptation, never a flat cut. A fingerprint that cannot travel was the building's, not the person's.
Illustrative engine read on the real portability layer (the Travel Ratio, the cross-country adaptability read, the actor-specific prior on a player's physical development and peak). Composite people, demonstration figures.
The honest measure is not how fit his players are, but how much fitter they became than the calendar explains.
Rate the person, not the building.
The Performance Lead read isolates the physical gain above maturation, attributes it to a named portable actor, and trusts it only once it has travelled.