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 Mackenzie McDonald the players push for greater prize money and welfare contributions from the grand slam tournaments could result in the difference between putting food on the table and making a decent living.After 10 years on the ATP Tour the 31-year-old American is not pleading poverty, but knows that life on the professional circuit can be a hand-to-...