FairValue

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Portrait of Mats Wieffer

Mats

Wieffer

RBNetherlands · Brighton & Hove Albion

№ 415381Elite €21.3M +0.16

Image: FootyLogos

Player dossierPremier League

MatsWieffer

RBRight-BackDefender

Club
Brighton & Hove Albion
League
Premier League
Nationality
Netherlands
Age
26
Height
189 cm
Foot
Right
Valued
3 Jun 2026

Reading the valuation

The market values Wieffer at €25M. Model A, which never saw Wieffer during training, estimates €21.3M: the market value is 17% above that estimate.

That is a factor of ×1.17. 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 €5.3M, 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.

▲ +0.16A €21.3M▲ +1.55B €5.3M
Pitch length is a log value scale fitted to this player's figures. ● observed · ◇ Model A · dashed ◇ Model B · each arc is a residual, log(observed) − log(estimate).
Apps
54
Minutes
2,988
Goals
3
Assists
8
Started
33/54
Min / app
55
Cards
14Y 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 Wieffer…

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 €25M

Checking API
EmergingEstablishedEliteWorld Class€2M€10M€30M€100k€1M€100MMarket €25MModel A €21.3M

Asking 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

Mats Wieffer's percentiles among defenders: Goals per 90 84th, Assists per 90 98th, Minutes, two years 53rd, Starts 16th, Minutes, last 365 days 59th, European club minutes 30th84thGoals98thAssists53rdMinutes16thStarts59thRecent30thEurope

Dashed ring: the defender median (50th percentile)

Assists per 90

Club assists per 90 minutes in the same window.

0.24 this player0.04 defender median98th percentile

0.00peer deciles · median line · this player ●0.58

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
€30M
May 2024
Model target
€25M
Jun 2026
Valuations
20
4 club changes
Jun 2026€25MBrighton & Hove AlbionValuation the model is trained to reproduce

Jun 2026: €25M, Brighton & Hove Albion. Dotted lines mark the €2M, €10M and €30M tier boundaries.

Show as a table
DateMarket valueClub
2019-01-21€25kFC Twente Enschede U21
2019-07-03€25kFC Twente Enschede U21
2020-08-12€25kSBV Excelsior
2020-10-24€75kSBV Excelsior
2020-12-31€225kSBV Excelsior
2021-10-12€275kExcelsior Rotterdam
2022-01-12€300kExcelsior Rotterdam
2022-06-23€400kExcelsior Rotterdam
2022-09-14€800kFeyenoord Rotterdam
2022-11-11€1MFeyenoord Rotterdam
2023-03-17€7MFeyenoord Rotterdam
2023-06-23€15MFeyenoord Rotterdam
2023-12-15€18MFeyenoord Rotterdam
2024-03-18€27MFeyenoord Rotterdam
2024-05-31€30MFeyenoord Rotterdam
2024-12-16€30MBrighton & Hove Albion
2025-03-18€27MBrighton & Hove Albion
2025-05-30€25MBrighton & Hove Albion
2025-12-09€25MBrighton & Hove Albion
2026-06-03€25MBrighton & Hove Albion

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
+0.160

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 →

Premier League555 players · median €18M

Valued above 63% of the 555 Premier League players.

€150k€1M€7.5M€50M€25MSee them in the Explorer →

Defenders, all leagues2,065 players · median €2M

Valued above 93% of the 2,065 defenders.

€20k€200k€2M€20M€25MSee them in the Explorer →

Where Wieffer appears

Watchlists and the comparison tray are kept in this browser only.

Near this valuation closest observed values: same league, then same position

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).