Lennard
Hartjes
CMNetherlands · Excelsior Rotterdam
Player dossierEredivisie
LennardHartjes
CMCentral MidfieldMidfield
- Club
- Excelsior Rotterdam
- League
- Eredivisie
- Nationality
- Netherlands
- Age
- 23
- Height
- 172 cm
- Foot
- Right
- Valued
- 28 May 2026
Reading the valuation
The market values Hartjes at €800k. Model A, which never saw Hartjes during training, estimates €1.1M: the market value is 30% below that estimate.
That is a factor of ×1.42. 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 €1.4M, 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
- 21
- Minutes
- 1,565
- Goals
- 1
- Assists
- 0
- Started
- 21/21
- Min / app
- 75
- Cards
- 1Y 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 Hartjes…
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 €800k
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 1,687 midfielders
Dashed ring: the midfielder median (50th percentile)
Starts
Share of appearances started rather than entered from the bench.
100% this player69% midfielder median99th 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
- €100k
- Oct 2021
- Peak
- €800k
- May 2026
- Model target
- €800k
- May 2026
- Valuations
- 12
- 3 club changes
May 2026: €800k, Excelsior Rotterdam. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2021-10-04 | €100k | Feyenoord Rotterdam |
| 2022-01-05 | €100k | Feyenoord Rotterdam |
| 2022-06-08 | €100k | Feyenoord Rotterdam |
| 2022-10-12 | €300k | Roda JC Kerkrade |
| 2023-07-04 | €500k | Feyenoord Rotterdam |
| 2023-12-15 | €500k | Excelsior Rotterdam |
| 2024-05-31 | €500k | Excelsior Rotterdam |
| 2024-12-10 | €600k | Excelsior Rotterdam |
| 2025-06-09 | €500k | Excelsior Rotterdam |
| 2025-12-02 | €450k | Excelsior Rotterdam |
| 2026-03-11 | €600k | Excelsior Rotterdam |
| 2026-05-28 | €800k | Excelsior Rotterdam |
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
- −0.353
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 40% of the 425 Eredivisie players.
See them in the Explorer →Midfielders, all leagues1,687 players · median €2M
Valued above 27% of the 1,687 midfielders.
See them in the Explorer →Where Hartjes appears
Watchlists and the comparison tray are kept in this browser only.
Near this valuation closest observed values: same league, then same position
- ClasieDMAZ Alkmaar · Eredivisie€800k
- Didillon-HödlGKWillem II Tilburg · Eredivisie€800k
- BranderhorstGKFortuna Sittard · Eredivisie€800k
- EdvardsenCFGo Ahead Eagles · Eredivisie€800k
- BadeljDMGenoa CFC · midfielders€800k
- CuadradoRMPisa Sporting Club · midfielders€800k
- DjuricicAMPanathinaikos · midfielders€800k
- MantalosAMAEK Athens · midfielders€800k
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).