Brynjólfur
Willumsson
CFIceland · FC Groningen
Player dossierEredivisie
BrynjólfurWillumsson
CFCentre-ForwardAttack
- Club
- FC Groningen
- League
- Eredivisie
- Nationality
- Iceland
- Age
- 25
- Height
- 185 cm
- Foot
- Right
- Valued
- 28 May 2026
EredivisieReading the valuation
The market values Willumsson at €900k. Model A, which never saw Willumsson during training, estimates €760k: the market value is 18% above that estimate.
That is a factor of ×1.18. 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 €1.6M, 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
- 58
- Minutes
- 2,253
- Goals
- 10
- Assists
- 1
- Started
- 19/58
- Min / app
- 39
- Cards
- 5Y 1R
Club matches, two years to the valuation date
The Valuation Journey
What moves Model A
Asking the prediction API to explain Model A for Willumsson…
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 €900k
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)
Goals per 90
Club goals per 90 minutes played in the two years to the valuation date.
0.40 this player0.26 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
- Dec 2018
- Peak
- €1.3M
- Oct 2025
- Model target
- €900k
- May 2026
- Valuations
- 15
- 2 club changes
May 2026: €900k, FC Groningen. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2018-12-15 | €25k | Breidablik Kópavogur |
| 2019-10-16 | €50k | Breidablik Kópavogur |
| 2020-12-01 | €100k | Breidablik Kópavogur |
| 2021-07-26 | €300k | Kristiansund BK |
| 2022-01-03 | €400k | Kristiansund BK |
| 2022-12-09 | €400k | Kristiansund BK |
| 2023-06-29 | €375k | Kristiansund BK |
| 2023-12-13 | €400k | Kristiansund BK |
| 2024-06-12 | €450k | Kristiansund BK |
| 2024-12-17 | €450k | FC Groningen |
| 2025-03-28 | €700k | FC Groningen |
| 2025-05-28 | €700k | FC Groningen |
| 2025-10-02 | €1.3M | FC Groningen |
| 2025-12-02 | €1.3M | FC Groningen |
| 2026-05-28 | €900k | FC Groningen |
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
- +0.170
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 44% of the 425 Eredivisie players.
See them in the Explorer →Attackers, all leagues1,583 players · median €2.5M
Valued above 28% of the 1,583 attackers.
See them in the Explorer →Where Willumsson appears
Watchlists and the comparison tray are kept in this browser only.
Near this valuation closest observed values: same league, then same position
- CrooijAMSparta Rotterdam · Eredivisie€900k
- AdewoyeCBFortuna Sittard · Eredivisie€900k
- GreimlCBNAC Breda · Eredivisie€900k
- OostingAMPEC Zwolle · Eredivisie€900k
- GiroudCFLOSC Lille · attackers€900k
- KvilitaiaCFFC Metz · attackers€900k
- BaldéLWAC Monza · attackers€900k
- KramerCFKonyaspor · attackers€900k
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).