Djokovic, 38, beat Tien, 6-1, 7-6, 6-2 to improve to 19-0 in US Open first-round matches, tying Roger Federer for first all-time. But he labored with low energy, a nasty blister on his right big toe and Tien’s level, especially in the second set.

Novak Djokovic wrapped up a routine victory over 50th-ranked World No. 50 Learner Tien to reach the US Open third round - but was made to look foolish by John McEnroe