There were also big wins for American men to raise hopes of a first home champion for 20 years.
Here, the PA news agency looks back at day five at the US Open.
Pic of the day
Match of the day
Djokovic maintained his bid for a record-equalling 24th Grand Slam title but he had to do it the hard way as he came back from two sets down to beat fellow Serb Laslo Djere.
It was the eighth time in his career the three-time champion Djokovic, who is aiming to match Australian Margaret Court’s tally of major wins, had successfully recovered from such a deficit.
He took a break after losing the second set and after his victory, said: “I did a pep talk in the mirror. It worked.”
Wozniacki fairytale continues
Wozniacki’s fairytale comeback continued as she came from behind to beat American Jennifer Brady.
The 33-year-old Dane, who retired more than three years ago and has had two children, won 4-6 6-3 6-1 and is through to the second week in only her third tournament since returning to tennis.
“As a competitor and an athlete you always want to win and you have to believe in yourself, but playing here on Arthur Ashe again is a dream come true,” she said.
“When I retired three years ago and having had two kids, I thought I’d just be here watching. What an honour this is.”
Quote of the day
The American dream is alive
The USA are waiting for a first home champion since Andy Roddick in 2003 and they will definitely have at least one quarter-finalist.
Tommy Paul is through to round four after beating Spain’s Alejandro Davidovich Fokina 6-1 6-0 3-6 6-3 and he will face fellow American Ben Shelton, who got past Aslan Karatsev of Russia 6-4 3-6 6-2 6-0.
Frances Tiafoe, the 10th seed, came from a set down to beat Frenchman Adrian Mannarino.
Not so many happy returns
A fourth American, Taylor Fritz, dropped just three games while pulverising Jakub Mensik 6-1 6-2 6-0 – on the Czech qualifier’s 18th birthday!
Neal Skupski and partner Wesley Koolhof are through to the third round of the doubles but Jamie Murray, alongside Michael Venus, bowed out as did Heather Watson with Anna Dalanina.
Men: Alejandro Davidovich Fokina (21), Adrian Mannarino (22).Women: Elise Mertens (32).
Who’s up next?
The British legion are back in action with Dan Evans taking centre stage, first up on Arthur Ashe against the defending champion and current world number one Carlos Alcaraz. Jack Draper and Katie Boulter will play their third-round matches, against Americans Michael Mmoh and Peyton Stearns, inside the imposing Grandstand Stadium and Cameron Norrie takes on Italian Matteo Arnaldi.