NEW YORK (AP) — Novak Djokovic shook off a back problem early in the match to beat Cam Norrie on Friday night and at 38 become the oldest man to reach the fourth round of the U.S. 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.

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