WIMBLEDON, England -- Novak Djokovic's smooth trip through the Wimbledon bracket got even easier Wednesday, when he moved into his record-tying 13th semifinal at the tournament via a walkover because his quarterfinal opponent, Alex de Minaur, withdrew with a hip injury.

De Minaur, an Australian who was seeded ninth at the All England Club, announced he was pulling out of the tournament hours before he and Djokovic were scheduled to play each other on Centre Court.

"Obviously not an announcement I wanted to make, by any means," de Minaur said at a news conference. "I'm devastated."

He explained that he heard a crack toward the end of his 6-2, 6-4, 4-6, 6-3 fourth-round victory over Arthur Fils on Monday. De Minaur walked gingerly to the net when that match ended, but he downplayed the severity of things when he spoke to the media afterward.

The walkover ties Djokovic with Roger Federer for the most Wimbledon semifinal appearances by a man in tournament history.

The second-seeded Djokovic had knee surgery less than a month before the start of Wimbledon, raising questions about whether he would even be able to try to earn his eighth championship at the grass-court major and add to his men's mark of 24 Grand Slam trophies.

But despite limitations in movement, the 37-year-old Djokovic has dropped only two sets while facing a qualifier in the first round, a wild-card entrant in the second and only one seeded player, No. 15 Holger Rune. Djokovic will now get three full days off before Friday's semifinals.

More eventful for Djokovic has been his interactions with some spectators at Centre Court. After beating Rune in straight sets Monday, Djokovic told fans that a group of them showed "disrespect" toward him with the way they were cheering.

Djokovic's next match will come against No. 13 Taylor Fritz of the United States or No. 25 Lorenzo Musetti of Italy. Fritz and Musetti were scheduled to play their quarterfinal Wednesday.

The extent of de Minaur's injury was clear from medical exams Tuesday, he said, but he wanted to at least give it a shot and try to play, if at all possible. But it was clear during a practice session Wednesday morning there was no way he could compete.

He said he barely could walk before a match that would have been de Minaur's first quarterfinal appearance at Wimbledon. He made it that far at the French Open last month, too.

"It's no secret that, at this stage of my career, this was the biggest match of my career. So wanted to do anything I could to play," de Minaur said. "I got the results yesterday. I knew what the results were yesterday. I still wanted to wake up today hoping that I would feel some sort of miracle and not feel it while I'm walking."

He said he was told that he could make his hip worse if he played another match.

"The problem with me going out and playing is that one stretch, one slide, one anything, can make this injury [recovery] go from three to six weeks to four months," de Minaur said. "It's too much to risk."

De Minaur's exit is the latest to come because of injury in Week 2 of the tournament. Players who stopped competing in the middle of fourth-round matches because they were hurt include No. 10 Grigor Dimitrov in the men's draw and No. 12 Madison Keys and No. 17 Anna Kalinskaya in the women's.