Marcos
Alonso
CBSpain · Celta de Vigo
Player dossierLaLiga
MarcosAlonso
CBCentre-BackDefender
- Club
- Celta de Vigo
- League
- LaLiga
- Nationality
- Spain
- Age
- 35
- Height
- 188 cm
- Foot
- Left
- Valued
- 5 Jun 2026
Reading the valuation
The market values Alonso at €1.2M. Model A, which never saw Alonso during training, estimates €1.6M: the market value is 23% below that estimate.
That is a factor of ×1.30. 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 €2.2M, 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
- 76
- Minutes
- 6,618
- Goals
- 5
- Assists
- 0
- Started
- 73/76
- Min / app
- 87
- Cards
- 18Y 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 Alonso…
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 €1.2M
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)
Minutes, last 365 days
Club minutes in the final year of the window: recent involvement, or the absence of it.
3,759 this player1,687 defender median98th 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
- €1.5M
- Jul 2010
- Peak
- €45M
- Oct 2018
- Model target
- €1.2M
- Jun 2026
- Valuations
- 44
- 6 club changes
Jun 2026: €1.2M, Celta de Vigo. Dotted lines mark the €2M, €10M and €30M tier boundaries.
Show as a table
| Date | Market value | Club |
|---|---|---|
| 2010-07-28 | €1.5M | Bolton Wanderers |
| 2011-02-01 | €2M | Bolton Wanderers |
| 2011-08-08 | €2M | Bolton Wanderers |
| 2012-02-06 | €1.5M | Bolton Wanderers |
| 2012-06-24 | €1.5M | Bolton Wanderers |
| 2013-03-02 | €1.5M | Bolton Wanderers |
| 2013-07-11 | €2M | ACF Fiorentina |
| 2014-01-15 | €2M | Sunderland AFC |
| 2014-11-08 | €3M | ACF Fiorentina |
| 2015-01-07 | €3M | ACF Fiorentina |
| 2015-07-01 | €2.8M | ACF Fiorentina |
| 2015-11-05 | €5.5M | ACF Fiorentina |
| 2016-01-04 | €8M | ACF Fiorentina |
| 2016-07-15 | €9M | ACF Fiorentina |
| 2016-10-24 | €13M | Chelsea FC |
| 2017-02-20 | €20M | Chelsea FC |
| 2017-06-28 | €25M | Chelsea FC |
| 2018-01-02 | €30M | Chelsea FC |
| 2018-03-23 | €35M | Chelsea FC |
| 2018-05-28 | €40M | Chelsea FC |
| 2018-10-17 | €45M | Chelsea FC |
| 2018-12-19 | €45M | Chelsea FC |
| 2019-06-13 | €40M | Chelsea FC |
| 2019-09-12 | €32M | Chelsea FC |
| 2019-12-10 | €25M | Chelsea FC |
| 2020-04-08 | €20M | Chelsea FC |
| 2020-07-30 | €18M | Chelsea FC |
| 2020-10-13 | €18M | Chelsea FC |
| 2020-12-17 | €13M | Chelsea FC |
| 2021-03-18 | €13M | Chelsea FC |
| 2021-06-08 | €12M | Chelsea FC |
| 2021-10-05 | €15M | Chelsea FC |
| 2021-12-23 | €15M | Chelsea FC |
| 2022-06-15 | €12M | Chelsea FC |
| 2022-11-07 | €9M | FC Barcelona |
| 2023-03-23 | €7M | FC Barcelona |
| 2023-06-13 | €5M | FC Barcelona |
| 2023-10-13 | €3M | FC Barcelona |
| 2023-12-22 | €3M | FC Barcelona |
| 2024-06-07 | €2M | FC Barcelona |
| 2024-12-27 | €1.8M | Celta de Vigo |
| 2025-06-09 | €1.5M | Celta de Vigo |
| 2025-12-12 | €1.4M | Celta de Vigo |
| 2026-06-05 | €1.2M | Celta de Vigo |
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
- −0.260
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 →Defenders, all leagues2,065 players · median €2M
Valued above 39% of the 2,065 defenders.
See them in the Explorer →Where Alonso appears
- TerminalLaLiga in the Player Explorer
- TerminalLaLiga on the League Landscape
Watchlists and the comparison tray are kept in this browser only.
Near this valuation closest observed values: same league, then same position
- BlindCBGirona FC · LaLiga€1.2M
- WitselDMGirona FC · LaLiga€1.2M
- SánchezSSSevilla FC · LaLiga€1.2M
- PortuRWGirona FC · LaLiga€1.2M
- CostaCB1.FSV Mainz 05 · defenders€1.2M
- LykogiannisLBBologna FC 1909 · defenders€1.2M
- StephensCBSouthampton FC · defenders€1.2M
- StenzelRBVfB Stuttgart · defenders€1.2M
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).