New York: World No.1 Novak Djokovic got his US Open tennis title defence off to a winning start with a topsy-turvy four-set triumph over Jerzy Janowicz at the Arthur Ashe Stadium, while Spanish tennis great Rafael Nadal cruised to victory in his first round match over Uzbekistan's Denis Istomin.

Top seed Djokovic prevailed 6-3, 5-7, 6-2, 6-1 to keep his bid for 10 straight semi-finals or better at the Flushing Meadows intact.