The Serbian was furious after failing to take a match point in the third set which allowed gutsy American Tennys Sandgren to pull one back.
It didn’t matter too much as the two time US Open champ upped his game in the fourth to set up a Saturday meeting with Frenchman Richard Gasquet thanks to a 6-1 6-3 6-7 6-2 win.
Djokovic, 31, is eyeing up a 14th slam title and arrived in New York as Wimbledon champ following a run at SW19 which saw Sandgren thrashed out of sight on the way.
But after almost falling foul of the steamy conditions in his opener before being forced to spend extra time on court by the American world No61, the super Serb hasn’t had it all his own way.
He moaned: “I just lost it mentally, I got p****ed off at something, myself , my game. I am not happy with the way I lost that concentration and composure.”
He took just 32 minutes to win the first set and didn’t take long to secure the second either.
The game was almost up only for Sandgren, who was praised by Djokovic afterwards for his fighting spirit, to save a match point and then bag the tie-break , much to the delight of the home fans.
An angry Djokovic, however, is a dangerous beast and just 33 minutes later, the 13 time slam winner was through.
He added: "I’m not happy with the way I lost my composure in the third set. I was getting stressed out. Credit to him but it’s not the first time I have done it.
"That how you learn and even with all my experience, I still make mistakes."
Meanwhile, it was a nightmare in New York for Aussie Open champ and No2 seed Caroline Wozniacki who was dumped out in straight sets in the second round by world No36 Lesia Tsurenko.
It was the Ukranian’s first ever win against a top five player — and a huge disappointment for the Danish star.
Maria Sharapova had a better day at the office though as the Russian, 31, beat Romania's Sorana Cirstea 6-2 7-5 despite 10 double faults.
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