Kaj de
Rooij
LWNetherlands · PEC Zwolle
Player dossierEredivisie
Kaj deRooij
LWLeft WingerAttack
- Club
- PEC Zwolle
- League
- Eredivisie
- Nationality
- Netherlands
- Age
- 25
- Height
- 184 cm
- Foot
- Right
- Valued
- 28 May 2026
Reading the valuation
The market values Rooij at €1M. Model A, which never saw Rooij during training, estimates €1.3M: the market value is 23% below that estimate.
That is a factor of ×1.30. 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 €4.2M, 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
- 55
- Minutes
- 2,454
- Goals
- 9
- Assists
- 6
- Started
- 24/55
- Min / app
- 45
- Cards
- 7Y 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 Rooij…
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 1,583 attackers
Dashed ring: the attacker median (50th percentile)
Minutes, last 365 days
Club minutes in the final year of the window: recent involvement, or the absence of it.
2,095 this player1,301 attacker median76th 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
- €25k
- Jan 2019
- Peak
- €1M
- Dec 2025
- Model target
- €1M
- May 2026
- Valuations
- 17
- 4 club changes
May 2026: €1M, PEC Zwolle. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2019-01-21 | €25k | FC Eindhoven U19 |
| 2019-07-03 | €25k | FC Eindhoven |
| 2020-01-17 | €300k | FC Eindhoven |
| 2020-06-29 | €400k | FC Eindhoven |
| 2020-08-12 | €475k | FC Eindhoven |
| 2020-10-24 | €575k | NAC Breda |
| 2020-12-31 | €575k | NAC Breda |
| 2021-10-12 | €500k | NAC Breda |
| 2022-01-12 | €475k | NAC Breda |
| 2022-06-23 | €450k | NAC Breda |
| 2023-07-04 | €375k | Without Club |
| 2024-05-31 | €350k | PEC Zwolle |
| 2024-12-17 | €350k | PEC Zwolle |
| 2025-05-28 | €350k | PEC Zwolle |
| 2025-10-02 | €600k | PEC Zwolle |
| 2025-12-02 | €1M | PEC Zwolle |
| 2026-05-28 | €1M | PEC Zwolle |
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
- −0.263
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 →Attackers, all leagues1,583 players · median €2.5M
Valued above 29% of the 1,583 attackers.
See them in the Explorer →Where Rooij 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
- DzekoCFFC Schalke 04 · attackers€1M
- DzyubaCFAkron Tolyatti · attackers€1M
- PedroRWSS Lazio · attackers€1M
- DjuricCFUS Cremonese · attackers€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).