Novak and Holding On

By the most obvious of measures, Novak Djokovic had the closest thing to a free ride into the quarterfinals of the U.S. Open. The field was basically cleared before he ever began. Rafael Nadal isn’t in New York. Neither is Roger Federer. Defending champ Dominic Thiem pulled out with a wrist injury. On the first day of the main draw, Andy Murray got knoc…