Novak Djokovic’s French Open campaign has been rocked by the sudden hospitalisation of his longtime friend and physio, Miljan Amanovic.

Amanovic has been in the 24-time grand slam champion’s inner circle for several years, and sits in his players’ box during matches.

The Serbian tennis legend provided an update on his friend on Friday (AEST), but wouldn’t be drawn into details of the “serious” health issue.

“Unfortunately, Miljan is in the hospital,” Djokovic said.

“He had a serious situation today and underwent surgery.

“I wouldn’t want to go into more detail than that.”

The 38-year-old said everyone in his team is worried.

“We’re all very concerned,” Djokovic added.

“He’s currently stable, but the situation isn’t ideal.

“He’ll have to stay in the hospital for a few days.

“We’re all worried. I hope everything will be alright.”

Later it was revealed that Amanovic had undergone sinus surgery a few weeks ago, and a complication had occurred where his nose started to bleed and could not be stopped by usual means.

And with Amanovic front-of-mind, Djokovic found it a bit of a slog to put away the eccentric Corentin Moutet 6-3, 6-2, 7-6 (7-1) in more than three hours to stay on course to go past the record of 24 grand slams that he currently shares with Margaret Court.

He had to survive a set point in the third set and also needed some medical treatment on the sore toes on his left foot.

“He had set point,” said Djokovic. “At that moment anything could happen but I stayed in the set. At the right time, I found a good serve.”

“Obviously, motivation now is to make more history,” added the phenomenon who’s looking in ominous form after his 100th title win in Geneva and will face either Canada’s Denis Shapovalov or Austrian Filip Misolic in round three.

The 38-year-old admitted it’s not as easy to back up from match to match anymore at his age, compounding the absence felt without his physio.

“Look, the recovery time is not much longer, I feel like,” he said.

“I mean, I’m pretty fit at the moment. I don’t feel like I have any major issues. Although it took me, like, almost an hour to deal with the blister and the bleeding that I had.

“So they had to use the injections and draw the blood out and then inject something to dry out the blister. So that was, you know, not really a pleasant process. But it is something that, you know, anyone who has blisters that are bleeding has to do it.

“So that’s why I’m also late with you guys, and I’m sorry for that. But I don’t think it’s going to be an issue for me to recover. I mean, three hours was a lot of running, straight sets, but a three-hour match is a good three-hour session.

“Good thing about slams obviously you have a day in between. So plenty of time to recover and get ready for the next one.”