Brain drain -- the emigration of skilled individuals toward higher-wage economies -- is a well-documented phenomenon, yet its aggregate economic cost remains difficult to quantify because individual productivity is rarely observed. We offer a novel angle on this measurement challenge by studying professional football, a global labour market in which every participant carries a publicly observable, consistently estimated market value. Using data on over 92,000 professional footballers worldwide from Transfermarkt, we identify nearly 20,000 players with multi-national eligibility and compute the implied transfer of human capital between countries. We find that the resulting "leg drain" disproportionately benefits wealthy European nations -- France alone gains over EUR3 billion in player value -- while African and Caribbean countries bear the largest losses relative to GDP. Italy is the single largest net loser in absolute terms, driven by the outflow of players with Italian heritage to Latin American national teams. A gravity model of bilateral flows reveals that former colonial ties are among the strongest predictors of leg drain intensity: countries with a colonial relationship to a major European footballing nation lose significantly more player value, even after controlling for population and income. These findings provide a transparent, quantifiable analogue to the broader brain drain debate and highlight how historical institutional links continue to shape global talent redistribution.