Stefan
Bell
CBGermany · 1.FSV Mainz 05
Player dossierBundesliga
StefanBell
CBCentre-BackDefender
- Club
- 1.FSV Mainz 05
- League
- Bundesliga
- Nationality
- Germany
- Age
- 34
- Height
- 192 cm
- Foot
- Right
- Valued
- 27 May 2026
Reading the valuation
The market values Bell at €600k. Model A, which never saw Bell during training, estimates €542k: the market value is 11% above that estimate.
That is a factor of ×1.11. 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 €391k, 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
- 41
- Minutes
- 2,775
- Goals
- 3
- Assists
- 3
- Started
- 31/41
- Min / app
- 68
- Cards
- 9Y 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 Bell…
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 €600k
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)
Goals per 90
Club goals per 90 minutes played in the two years to the valuation date.
0.10 this player0.03 defender median86th 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
- €150k
- Jul 2010
- Peak
- €6M
- Jul 2016
- Model target
- €600k
- May 2026
- Valuations
- 37
- 3 club changes
May 2026: €600k, 1.FSV Mainz 05. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2010-07-04 | €150k | 1.FSV Mainz 05 |
| 2010-07-07 | €1M | 1.FSV Mainz 05 |
| 2010-08-28 | €1.5M | TSV 1860 Munich |
| 2011-01-12 | €1.5M | TSV 1860 Munich |
| 2011-06-04 | €1.5M | TSV 1860 Munich |
| 2011-10-18 | €1.3M | Eintracht Frankfurt |
| 2012-01-16 | €1M | 1.FSV Mainz 05 |
| 2012-06-29 | €800k | 1.FSV Mainz 05 |
| 2013-01-13 | €500k | 1.FSV Mainz 05 |
| 2013-06-30 | €600k | 1.FSV Mainz 05 |
| 2014-02-12 | €1.5M | 1.FSV Mainz 05 |
| 2014-07-10 | €3.5M | 1.FSV Mainz 05 |
| 2015-02-04 | €3.5M | 1.FSV Mainz 05 |
| 2015-07-01 | €4M | 1.FSV Mainz 05 |
| 2016-02-15 | €5M | 1.FSV Mainz 05 |
| 2016-07-22 | €6M | 1.FSV Mainz 05 |
| 2017-02-07 | €6M | 1.FSV Mainz 05 |
| 2017-06-19 | €6M | 1.FSV Mainz 05 |
| 2017-12-28 | €6M | 1.FSV Mainz 05 |
| 2018-06-05 | €6M | 1.FSV Mainz 05 |
| 2018-12-18 | €6M | 1.FSV Mainz 05 |
| 2019-06-05 | €3.5M | 1.FSV Mainz 05 |
| 2019-12-17 | €3.5M | 1.FSV Mainz 05 |
| 2020-03-11 | €1.8M | 1.FSV Mainz 05 |
| 2020-04-08 | €1.4M | 1.FSV Mainz 05 |
| 2021-02-10 | €1.4M | 1.FSV Mainz 05 |
| 2021-06-09 | €2M | 1.FSV Mainz 05 |
| 2021-12-22 | €2.5M | 1.FSV Mainz 05 |
| 2022-06-09 | €2.5M | 1.FSV Mainz 05 |
| 2022-11-09 | €2.5M | 1.FSV Mainz 05 |
| 2023-06-22 | €2M | 1.FSV Mainz 05 |
| 2023-12-14 | €1M | 1.FSV Mainz 05 |
| 2024-05-29 | €800k | 1.FSV Mainz 05 |
| 2024-12-20 | €800k | 1.FSV Mainz 05 |
| 2025-06-05 | €800k | 1.FSV Mainz 05 |
| 2025-12-19 | €600k | 1.FSV Mainz 05 |
| 2026-05-27 | €600k | 1.FSV Mainz 05 |
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
- +0.102
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 →Bundesliga451 players · median €5M
Valued above 2% of the 451 Bundesliga players.
See them in the Explorer →Defenders, all leagues2,065 players · median €2M
Valued above 22% of the 2,065 defenders.
See them in the Explorer →Where Bell appears
Watchlists and the comparison tray are kept in this browser only.
Near this valuation closest observed values: same league, then same position
- JungCBSC Freiburg · Bundesliga€600k
- TrimmelRB1.FC Union Berlin · Bundesliga€600k
- MetsCBFC St. Pauli · Bundesliga€600k
- BlaswichGKBayer 04 Leverkusen · Bundesliga€700k
- SilvestriRBBologna FC 1909 · defenders€600k
- YalçınCBEyüpspor · defenders€600k
- LópezCBGirona FC · defenders€600k
- BuatuCBGil Vicente FC · defenders€600k
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).