*Djokovic - Fritz: 6h, 3/9, Hanoi time.

"Honestly, I've never worried about my body like this before," Djokovic told ESPN after the fourth round on 1/9. "Even though I take meticulous care of my body, spending hours on recovery, I still can't fight time."

Djokovic during his match against Struff, in the fourth round of the US Open, at Arthur Ashe Stadium, New York on 1/9. Photo: *Reuters*

In his third-round victory over Cameron Norrie, Djokovic showed signs of lower back pain in the first set after lunging to save a point. Before the end of the first set, Djokovic left Arthur Ashe Stadium for medical attention. The former world number 1 continued to require assistance from the doctor early in the second set. From that point on, Djokovic played more freely.

Despite winning 3-0 against Jan-Lennard Struff in the fourth round, Djokovic still showed signs of discomfort. After the first set, a doctor had to come onto the court to treat his right shoulder and neck. In the next set, the Serbian player needed further treatment for his right arm.

"Things have changed; I have to find ways to train and compete that are more suitable for my current physical condition," Djokovic added. "Sometimes I don't practice between matches to give my body more time to rest, because recovery is now more important to me than hitting balls. My team and I are constantly discussing when to rest and when to train."

Djokovic has shown signs of physical discomfort in earlier matches as well. In his opening match, the 38-year-old looked tired and depleted despite his 3-0 win over Learner Tien. In the second round, Djokovic again displayed physical issues after a four-set match against Zachary Svajda.

"Compared to before, I need more time each day to keep up with today's generation," Djokovic said about recovery at current tournaments. "Whether it's on-site recovery, using various machines, nutrition, or sleep, my team and I have to calculate and balance everything. It's all important when you're participating in lengthy events."

Djokovic also said there's no guaranteed solution for achieving his desired physical state, as the body's reaction each day is unpredictable. The 24-time Grand Slam champion now faces Taylor Fritz in the US Open quarterfinals. Djokovic has won all 10 of their previous encounters.

Vy Anh