Boy
Kemper
LBNetherlands · NAC Breda
Player dossierEredivisie
BoyKemper
LBLeft-BackDefender
- Club
- NAC Breda
- League
- Eredivisie
- Nationality
- Netherlands
- Age
- 26
- Height
- 185 cm
- Foot
- Left
- Valued
- 28 May 2026
Reading the valuation
The market values Kemper at €1M. Model A, which never saw Kemper during training, estimates €1.5M: the market value is 32% below that estimate.
That is a factor of ×1.47. Model A's typical held-out miss is ×1.50 either way, so this gap is within its usual error.
Without league and club, Model B estimates €7.2M, further from the market. Model B is usually further off (typical miss ×2.07): league and club explain much of how the market prices players.
A gap describes the model's arithmetic for this player's inputs, not what the player is worth.
- Apps
- 62
- Minutes
- 5,322
- Goals
- 7
- Assists
- 7
- Started
- 61/62
- Min / app
- 86
- Cards
- 12Y 0R
Club matches, two years to the valuation date
The Valuation Journey
What moves Model A
Asking the prediction API to explain Model A for Kemper…
SHAP describes the model's arithmetic for this player's inputs, not what causes market value. Model B can be explained only by the live service; Model A also has a published explanation for the research players.
Model A vs Model B against the observed €1M
Checking APIAsking the prediction API…
Held-out estimates come from cross-validation, with this player outside the training data: the honest comparison. Served models were refitted on every player, this one included, so they sit closer to the market. Shaded band: Model A's typical miss (×1.50 either way).
Player traitspercentiles vs 2,065 defenders
Dashed ring: the defender median (50th percentile)
Starts
Share of appearances started rather than entered from the bench.
98% this player83% defender median93rd percentile
No passing, progression or defensive actions exist in the dataset, so no trait claims to measure them.
Valuation history every Transfermarkt valuation on record
- First valuation
- €50k
- Aug 2017
- Peak
- €1M
- May 2026
- Model target
- €1M
- May 2026
- Valuations
- 19
- 3 club changes
May 2026: €1M, NAC Breda. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2017-08-18 | €50k | Ajax Amsterdam U19 |
| 2018-03-01 | €150k | Ajax Amsterdam U19 |
| 2018-06-29 | €150k | Ajax Amsterdam U19 |
| 2019-01-21 | €150k | Ajax Amsterdam U21 |
| 2019-07-03 | €150k | Ajax Amsterdam U21 |
| 2020-06-29 | €400k | Ajax Amsterdam U21 |
| 2020-10-14 | €400k | ADO Den Haag |
| 2021-05-19 | €450k | ADO Den Haag |
| 2021-10-12 | €375k | ADO Den Haag |
| 2022-01-12 | €400k | ADO Den Haag |
| 2022-06-23 | €450k | ADO Den Haag |
| 2023-07-04 | €500k | NAC Breda |
| 2024-01-08 | €500k | NAC Breda |
| 2024-06-10 | €500k | NAC Breda |
| 2024-10-14 | €650k | NAC Breda |
| 2024-12-17 | €750k | NAC Breda |
| 2025-05-28 | €850k | NAC Breda |
| 2025-12-02 | €850k | NAC Breda |
| 2026-05-28 | €1M | NAC Breda |
Audit context group-level, not about this player
- Audit group
- UEFA
- Population gap, Model A
- +0.093 95% CI +0.063 to +0.124
- This player, market vs held-out A
- −0.387
The group comes from first-listed citizenship and is never a model input. Across the population, non-UEFA players' market values sit about 10% above Model A's held-out estimates, relative to UEFA players in the same leagues. One player's residual says nothing about that pattern (typical miss ×1.50), and none of it is evidence of discrimination: the target may itself be biased. Open the Fairness Audit
In context observed value among comparable players in this build
All players in the Terminal →Eredivisie425 players · median €1M
Valued above 46% of the 425 Eredivisie players.
See them in the Explorer →Defenders, all leagues2,065 players · median €2M
Valued above 35% of the 2,065 defenders.
See them in the Explorer →Where Kemper appears
Watchlists and the comparison tray are kept in this browser only.
Near this valuation closest observed values: same league, then same position
- UnnerstallGKFC Twente Enschede · Eredivisie€1M
- HallerCFFC Utrecht · Eredivisie€1M
- OvereemDMSC Heerenveen · Eredivisie€1M
- NamliRWPEC Zwolle · Eredivisie€1M
- OtamendiCBSL Benfica · defenders€1M
- AzpilicuetaCBSevilla FC · defenders€1M
- KaravaevRBDynamo Kyiv · defenders€1M
- BerchicheLBAthletic Bilbao · defenders€1M
Counts and ranks of observed Transfermarkt values only; model errors are never ranked here. Full player export: Every player in the modelling population (D-011).