‘Grand slams are the engine to make a living’: Mackenzie McDonald on why players still compete when injured

American talks life on the professional circuit and those making sacrifices for a pay cheque, often compromising physical and mental welfareFor the American tennis veteran Mackenzie McDonald the players’ ongoing push for greater prize money and welfare contributions from the grand slam tournaments could result in the difference between simply putting food on the table and making a decent living.After 10 years on the ATP Tour the 31-year-old is not pleading poverty but knows from personal experience that life on the professional circuit can be a hand-to-mouth existence, with players’ physical and mental welfare often compromised due to their desperation to get back on court.