Paris, France - Novak Djokovic was "hoping for the best" Thursday that his troublesome right knee won't derail his dreams of finally winning Olympic gold.

Djokovic aggravated the knee, which required surgery in June, during his 6-3, 7-6 (7/3) win over Stefanos Tsitsipas in the quarter-finals on Thursday at Roland Garros.

The 37-year-old needed on-court treatment and a pain-killer after slipping on the baseline of Court Philippe Chatrier and hobbling gingerly around the arena.

He recovered from 0-4 and then 2-5 down, saving three set points in the ninth game, before racing away with the tie-break.

The Serb faces Italy's Lorenzo Musetti on Friday in the last four.

"I'm concerned about the state of the knee. I cannot give you exact information because I don't have it. I have to go and examine the knee with medical staff and then let's see," said Djokovic.

"I'm playing at 7:00 PM tomorrow, which gives me slightly more time. But I'm hoping I can be ready and be optimistic. I have to be."

He added: "The anti-inflammatory helped. But that effect is going to fade away, so I'll have probably a more realistic picture tomorrow and then hope for the best."

The 24-time Grand Slam title winner is still looking for a first Olympic gold medal having so far managed just a bronze in Beijing in 2008.

He will be playing in his fourth Olympic semi-final.

"I will have to be 100% in my own abilities and physically be fit, to be able to be run with him in order for me to try to win the match. I know that it's going to be tough," Djokovic added of the clash with Musetti.

The Serb tore the meniscus in his right knee at the French Open in June, which forced him to withdraw from the quarter-finals.

He underwent immediate surgery and miraculously went all the way to the Wimbledon final, where he was defeated by Spain's Carlos Alcaraz.

"It's good that I managed to get it done in straight sets and finish the match tonight," he told a TV interviewer on court after defeating Tsitsipas.

"But I also finished my fourth-round match at the French Open and then discovered that I had torn my meniscus."

"I need to see what happens now. I don't know what to say. It's day by day. I hope I can be physically fit for tomorrow."

Djokovic has defeated Musetti six times in seven meetings, including in the semi-finals of Wimbledon.

Musetti became the first Italian to reach an Olympic semi-final earlier Thursday when he knocked out defending champion Alexander Zverev.

For Tsitsipas, Thursday's result was another sobering experience when facing Djokovic. He famously lost the 2021 French Open final on the same court to Djokovic from two sets up.

Djokovic also got the better of him in the 2023 Australian Open final. It has been five years since Tsitsipas last defeated the Serb.

"I learned once again that it's not over. It's not really happening until you really close it out," said Tsitsipas.

"It's probably one of the very few times in my career that I was a double break up and lost a set. It's definitely disappointing because I was feeling great."