Supplementary file 1_Injury characteristics and pre- to post-injury market-value change in professional football: a retrospective cohort study of 12,948 injury episodes.docx

Introduction<p>Player market value is a key indicator of a professional football player’s sporting and economic worth, yet how injury characteristics relate to the change in valuation after an injury remains poorly understood.</p>Methods<p>This retrospective cohort study examined the association between injury characteristics and the pre- to post-injury change in market value using Transfermarkt data. The cohort comprised the complete injury histories (July 2008 to August 2024) of the 2,624 players listed in the 2024 squads of the English, Spanish, Italian, German and French top divisions; 12,948 injury episodes from 2,061 players had a valuation in effect 120 days before the injury start and a valuation update after the 120 days following the injury end, and the outcome was the percentage change between these two valuations.

Kruskal–Wallis tests with effect sizes, Dunn pairwise comparisons and linear regression models with player-clustered standard errors were used; age interactions were tested with joint Wald tests, and an exploratory matched-control comparison assessed differences in log-value change between injured players and injury-free player-periods matched on league, position group, age and baseline market value.</p>Results<p>The median change was 0.0% (interquartile range −25.0 to 66.7) and the mean 64.7%.