Appearing to be affected by neck and arm injuries in the early stages of his quarterfinal match against Pablo Carreno Busta, Djokovic dug deep to overcome the Spaniard 4-6, 6-2, 6-3, 6-4 on Wednesday.In what was a rematch of the meeting between the pair at the US Open last month where Djokovic was disqualified for hitting a line judge with a ball, the Serbian grimaced as he lost the first set, making an uncharacteristic 16 unforced errors.”Well, I definitely didn’t feel great coming into the court today,” Djokovic told reporters. “Few things happened in the warm-up. I had to deal with those physical issues coming onto the court.”Djokovic arrived Court Philippe-Chatrier with tape on the back of his neck and repeatedly showed his discomfort, pulling at his left bicep during the opening hour, while trainer Paul Ness helped the world No. 1 after the first set and early in the second to massage his neck and left arm.”Obviously, I’m still in the tournament, so I don’t want to reveal too much,” Djokovic said of his injuries.”I’m feeling OK. I think as the match progressed, I warmed up my body, and the pain kind of faded away. It allowed me to play better and better and feel better.”Having had some attention from his physio — and after eating some dates — Djokovic looked more comfortable, eventually battling to victory after three hours and 10 minutes.His win sees the 17-time grand slam winner into the last four of a Grand Slam for the 38th time.”These four tournaments, the four grand slams matter the most probably in tennis history. [They are] the most popular tennis events in the world. A lot of kids, when they take a racquet in their hands, they dream of winning Roland Garros, Wimbledon, the Australian Open and the US Open,” Djokovic said. “I’ve been very fortunate to play very well throughout my career in grand slams.Visit CNN.com/sport for more news, features, and videos”It’s not only my success. It’s the success of my team, my family that has been supporting me throughout my whole life. It wasn’t easy growing up in a war-torn country and without any tennis guidance or tennis tradition, really. To succeed in this beautiful sport means a lot to me. I try to be conscious of every achievement, be grateful for it and put things in perspective.”Djokovic will next face world sixth seed Stefanos Tsitsipas in the semifinals, a player who has beaten him twice in five meetings, after the Greek beat Andrey Rublev in straight sets in the quarterfinals.Djokovic, who is the 2016 French Open champion, is seeking to become the first man in the Open era to win all four grand slams twice.