NEW YORK — Novak Djokovic shook off a back problem early in the match to beat Cam Norrie on Friday night and at 38 to become the oldest man to reach the fourth round of the US Open since Jimmy Connors was the same age in 1991. Djokovic pulled away to win 6-4, 6-7 (4), 6-2, 6-3, helped by hitting 18 aces in what he said was his best serving performance of the tournament. READ: Novak Djokovic makes US Open third round for 19th time The 24-time Grand Slam champion seemed in jeopardy of matching his earliest exit in Flushing […]... Keep on reading: US Open: Novak Djokovic shakes off back issue, enters fourth round