David Ferrer is having arguably the best years of career at the age of 29-30. This is remarkable, ESPECIALLY for a grinder like him. Ferrer seems to have lost none of the speed that made him such a formidable opponent in his mid 20's, and even seems to improved his already legendary stamina. Has this ever happened before? Typically, grinders burn out in their mid 20's. What is Ferrer's secret?