Konstantinos
Kostoulas
CBGreece · OFI Crete
Player dossierSuper League
KonstantinosKostoulas
CBCentre-BackDefender
- Club
- OFI Crete
- League
- Super League
- Nationality
- Greece
- Age
- 21
- Height
- 187 cm
- Foot
- Right
- Valued
- 4 Jun 2026
Reading the valuation
The market values Kostoulas at €800k. Model A, which never saw Kostoulas during training, estimates €1.2M: the market value is 34% below that estimate.
That is a factor of ×1.52. Model A's typical held-out miss is ×1.50 either way, so this gap is larger than 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
- 26
- Minutes
- 1,981
- Goals
- 0
- Assists
- 1
- Started
- 23/26
- Min / app
- 76
- Cards
- 5Y 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 Kostoulas…
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 2,065 defenders
Dashed ring: the defender median (50th percentile)
Starts
Share of appearances started rather than entered from the bench.
88% this player83% defender median65th 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
- Sept 2023
- Peak
- €800k
- Jun 2026
- Model target
- €800k
- Jun 2026
- Valuations
- 9
- 3 club changes
Jun 2026: €800k, OFI Crete. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2023-09-21 | €25k | Olympiacos Piraeus B |
| 2023-12-28 | €25k | Olympiacos Piraeus B |
| 2024-03-13 | €75k | Olympiacos Piraeus B |
| 2024-05-23 | €175k | Olympiacos Piraeus B |
| 2024-12-19 | €300k | Rio Ave FC U23 |
| 2025-05-30 | €500k | Rio Ave FC |
| 2025-12-12 | €450k | OFI Crete |
| 2026-03-06 | €500k | OFI Crete |
| 2026-06-04 | €800k | OFI Crete |
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
- −0.421
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 →Super League356 players · median €600k
Valued above 60% of the 356 Super League players.
See them in the Explorer →Defenders, all leagues2,065 players · median €2M
Valued above 29% of the 2,065 defenders.
See them in the Explorer →Where Kostoulas appears
Watchlists and the comparison tray are kept in this browser only.
Near this valuation closest observed values: same league, then same position
- DjuricicAMPanathinaikos · Super League€800k
- MantalosAMAEK Athens · Super League€800k
- JønssonDMAEK Athens · Super League€800k
- RodineiRBOlympiacos Piraeus · Super League€800k
- CaraccioloCBPisa Sporting Club · defenders€800k
- BianchettiCBUS Cremonese · defenders€800k
- WidmerRB1.FSV Mainz 05 · defenders€800k
- WinckRBKasimpasa · defenders€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).