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.

Tennis icon Novak Djokovic once again etched his name in the record books after his opening win over Learner Tien in the US Open.

As a tennis veteran, Djokovic will know match sharpness is very different to playing practice sets, so it was no surprise that his physical levels collapsed mid-way through his match against the young and hungry Tien.