Transfer relationships and regulations

[Getty Images]Unai Emery has insisted that there are no "good relations" between Chelsea and Aston Villa after a series of transfers between the clubs.On Sunday, Argentina goalkeeper Emiliano Martinez joined Chelsea from Aston Villa, completing the eighth deal between the clubs in the past four years.Martinez's move to Stamford Bridge comes after Nicolas Jackson's transfer the other way last week.No two Premier League clubs have exchanged more players, on permanent or loan deals, in the past fou