Djokovic wants to become the first man since Rod Laver in 1969 to win the Grand Slam on the calendar, but said he thought he heard cheers from the crowd when he survived a scare to 6-1 6-7 6-2 6- 1 to win.
“I honestly didn’t know what they were chanting. I thought they were yelling,” he told reporters after the game.
“I don’t know, it wasn’t the ideal atmosphere for me to tell you that. But I’ve been in these specific spheres before, so I knew how to deal with it.
“I mean, of course you always want to have people behind you, but that’s not always possible.
“That’s all I can say. I mean, I don’t know. I’ve been focusing on myself and what to do. I think I just need to see how it feels on the pitch and try to keep it together . That’s all I can do.”
It is unclear whether fans booed the Serb or chanted “Rune” in support of his Danish opponent.
Rune himself was confused by what he initially thought was booing, but said he was delighted when he realized that many were just cheering for the underdog.
“Actually, at one point they were cheering for me; at another point they were cheering. I was like, ‘What’s going on?'” he told reporters.
“Suddenly after the game I heard they say ‘Rune’. When I heard that I was happy because I didn’t understand it in the game. Like I said, it was an amazing audience, the best thing I ever had in my life have felt.”
‘I’m very excited’
Djokovic has already won the Australian Open, French Open and Wimbledon this year and needs just one more win at the final slam of the year to complete the epic feat.
Triumph at the US Open would also take the 34-year-old to 21 major titles, surpassing Roger Federer and Rafael Nadal, who each have 20 majors to their name.
“Writing history in this sport is of the utmost importance to me, especially at this stage of my career. And playing and trying to win as many grand slams as possible is the top priority in my tennis season.”
He said he was “out of gas” at the Summer Olympics but is eager to get back on track after a hiatus.
“Pressure is a privilege. I’ve grown and developed a little bit throughout my career to really handle pressure in the right way,” he added. “But nothing is guaranteed.
“I like adversity. I like expectations and pressure and, you know, in a way it brings out the best in me. So, yeah, hopefully I can have some great weeks.”