Marlon
Fossey
RBUnited States · Standard Liège
Player dossierPro League
MarlonFossey
RBRight-BackDefender
- Club
- Standard Liège
- League
- Pro League
- Nationality
- United States
- Age
- 27
- Height
- 179 cm
- Foot
- Right
- Valued
- 4 Jun 2026
Pro LeagueReading the valuation
The market values Fossey at €3.5M. Model A, which never saw Fossey during training, estimates €1.4M: the market value is 149% above that estimate.
That is a factor of ×2.49. 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 €1.2M, 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
- 49
- Minutes
- 3,996
- Goals
- 1
- Assists
- 3
- Started
- 48/49
- Min / app
- 82
- Cards
- 4Y 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 Fossey…
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 €3.5M
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 median92nd 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
- €250k
- Jun 2022
- Peak
- €5M
- Jun 2025
- Model target
- €3.5M
- Jun 2026
- Valuations
- 11
- 1 club change
Jun 2026: €3.5M, Standard Liège. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2022-06-15 | €250k | FC Fulham U23 |
| 2022-11-04 | €1M | Standard Liège |
| 2023-03-22 | €2M | Standard Liège |
| 2023-06-09 | €2.5M | Standard Liège |
| 2023-12-19 | €3M | Standard Liège |
| 2024-06-04 | €3M | Standard Liège |
| 2024-10-02 | €4M | Standard Liège |
| 2024-12-11 | €4M | Standard Liège |
| 2025-06-12 | €5M | Standard Liège |
| 2025-12-10 | €4M | Standard Liège |
| 2026-06-04 | €3.5M | Standard Liège |
Audit context group-level, not about this player
- Audit group
- non-UEFA
- Population gap, Model A
- +0.093 95% CI +0.063 to +0.124
- This player, market vs held-out A
- +0.913
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 →Pro League350 players · median €1.8M
Valued above 73% of the 350 Pro League players.
See them in the Explorer →Defenders, all leagues2,065 players · median €2M
Valued above 63% of the 2,065 defenders.
See them in the Explorer →Where Fossey appears
Watchlists and the comparison tray are kept in this browser only.
Near this valuation closest observed values: same league, then same position
- ReynoldsRBKVC Westerlo · Pro League€3.5M
- SayyadmaneshRWKVC Westerlo · Pro League€3.5M
- PaskotsiCBKAA Gent · Pro League€3.5M
- HuertaLWRSC Anderlecht · Pro League€3.5M
- SpinazzolaLBSSC Napoli · defenders€3.5M
- DunkCBBrighton & Hove Albion · defenders€3.5M
- KempfCBComo 1907 · defenders€3.5M
- KlostermannCBRB Leipzig · defenders€3.5M
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).