Is record-breaking Djokovic robust enough to keep rolling back years?

The 38-year-old is in the US Open quarter-finals, but his body has lately struggled in the latter stages of grand slamsAlmost every time Novak Djokovic has competed in a grand slam tournament this year, a record has fallen. In New York alone, he became the oldest man in more than three decades to reach the fourth round of the US Open, then he repeated the trick by winning that fourth-round match. Djokovics straight-sets victory against Jan Lennard Struff established the 38-year-old as the oldest...