FairValue

Checking model

Esc

  • EnvironmentOverviewWhat FairValue measures, what it found, where to go next.
  • EnvironmentTerminalExplore, compare and track players; market, league and model views.
  • EnvironmentStoriesValuations, head-to-heads and research findings, told as stories.
  • TerminalPlayer ExplorerSearch, filter and sort the player export.
  • TerminalComparison StudioTwo to four players on one scale.
  • TerminalWatchlistsNamed collections, kept in this browser.
  • TerminalMarket LandscapeHow observed value is distributed, and where the model drifts.

↑ ↓ to move · Enter to open · Esc to closeLoading player index…

Joël

Drommel

GKNetherlands · Sparta Rotterdam

№ 333640Established €1.1M +1.28

Player dossierEredivisie

JoëlDrommel

GKGoalkeeperGoalkeeper

Club
Sparta Rotterdam
League
Eredivisie
Nationality
Netherlands
Age
29
Height
192 cm
Foot
Right
Valued
28 May 2026

Reading the valuation

The market values Drommel at €4M. Model A, which never saw Drommel during training, estimates €1.1M: the market value is 258% above that estimate.

That is a factor of ×3.58. 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 €2.8M, closer to the market here, although it is usually further off (typical miss ×2.07).

A gap describes the model's arithmetic for this player's inputs, not what the player is worth.

▲ +1.28A €1.1M▲ +0.37B €2.8M
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
40
Minutes
3,585
Started
39/40
Min / app
90
Cards
1Y 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 Drommel…

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 €4M

Checking API
EmergingEstablishedEliteWorld Class€2M€10M€30M€100k€1M€100MMarket €4MModel A €1.1M

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 485 goalkeepers

Joël Drommel's percentiles among goalkeepers: Minutes, two years 64th, Starts 18th, Minutes, last 365 days 80th, European club minutes 65th64thMinutes18thStarts80thRecent65thEurope

Dashed ring: the goalkeeper median (50th percentile)

Minutes, last 365 days

Club minutes in the final year of the window: recent involvement, or the absence of it.

3,060 this player1,560 goalkeeper median80th percentile

0peer deciles · median line · this player ●4,970

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
Aug 2014
Peak
€4.5M
Oct 2021
Model target
€4M
May 2026
Valuations
32
3 club changes
May 2026€4MSparta RotterdamValuation the model is trained to reproduce

May 2026: €4M, Sparta Rotterdam. Dotted lines mark the €2M, €10M and €30M tier boundaries.

Show as a table
DateMarket valueClub
2014-08-15€25kFC Twente Enschede U21
2015-02-21€50kFC Twente Enschede U21
2015-07-01€50kFC Twente Enschede
2015-11-11€500kFC Twente Enschede
2016-02-05€500kFC Twente Enschede
2016-07-15€500kFC Twente Enschede
2017-01-18€500kFC Twente Enschede
2017-06-07€500kFC Twente Enschede
2018-01-17€600kFC Twente Enschede
2018-06-12€500kFC Twente Enschede
2019-01-21€350kFC Twente Enschede
2019-03-25€400kFC Twente Enschede
2019-07-03€750kFC Twente Enschede
2019-09-19€1.3MFC Twente Enschede
2019-12-18€1.3MFC Twente Enschede
2020-04-08€1MFC Twente Enschede
2020-10-14€2.5MFC Twente Enschede
2021-01-06€4MFC Twente Enschede
2021-05-19€4MFC Twente Enschede
2021-10-04€4.5MPSV Eindhoven
2022-01-05€4.5MPSV Eindhoven
2022-06-08€3.5MPSV Eindhoven
2022-09-14€3MPSV Eindhoven
2022-11-11€3MPSV Eindhoven
2023-06-23€2.5MPSV Eindhoven
2023-12-15€2.5MPSV Eindhoven
2024-05-31€2.5MPSV Eindhoven
2024-12-17€2MPSV Eindhoven
2025-05-28€1.5MPSV Eindhoven
2025-12-02€2MSparta Rotterdam
2026-03-11€2.5MSparta Rotterdam
2026-05-28€4MSparta Rotterdam

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
+1.275

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 76% of the 425 Eredivisie players.

€75k€500k€3M€20M€4MSee them in the Explorer →

Goalkeepers, all leagues485 players · median €1M

Valued above 75% of the 485 goalkeepers.

€20k€200k€2M€20M€4MSee them in the Explorer →

Where Drommel 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).