The transfer fees clubs pay to sign top players now top €4 billion a year but much of the money has been flowing out of the game. A small group of wealthy investors including Russian oligarchs, English racehorse owners and a former billionaire gold miner have seized the opportunity to enter this booming market. Some have moved in on the territory of banks and lent money to clubs in exchange for a share in fees generated by Cristiano Ronaldo, Neymar and dozens more of today's stars. Others have...