Novak Djokovic was today undergoing a scan on his damaged knee to see whether he is fit to continue in this year’s French Open.

Djokovic came through a second successive five-setter to beat Francisco Cerundolo 6-1, 5-7, 3-6, 7-5, 6-3 and book a quarter-final against Casper Ruud, a repeat of last year’s final at Roland Garros.

But the 37-year-old warned he had come close to withdrawing midway through the match against the No23 and blamed the slippery court for exacerbating an already existing problem.

Following his latest marathon encounter, the Serbian said: “I guess we’ll do some more screening and check-ups.

“We have done some with the doctor right now after the match. Some positive news but also some maybe concerns, so let’s see [on Tuesday]. I can’t tell you more about it at the moment.”

Djokovic had begun the match wearing tape behind his right knee and needed to have a medical timeout for on-court physio treatment early in the second set.

Telling the medical official he had “screwed up” his knee, he added: “I’m slipping and sliding all the time.”

He was given painkillers as he was later in the match but needed subsequent treatment and said it was not until the fifth set where he finally began to be playing pain free.

“I had slight discomfort in the right knee for a couple of weeks but it was not an injury which was concerning until today,” he said.

“The late finish did not help the sleeping, the biorhythm and recovery but I actually felt good in the circumstances. Then I slipped, one of the many times I slipped, and that affected the knee. I started feeling the pain.

“At one point, I didn’t know if I should continue. The reason why I continued was because I wanted to see if an extra anti-inflammatory was going to kick in and reduce the limitations, which is what happened.

“I don’t know… if I’ll be able to step out on the court and play. I hope so. Let’s see what happens.”

While Djokovic avoided another late finish, Alexander Zverev’s match against Holger Rune didn’t finish until 1.40am this morning.

Zverev, who is in the midst of an ongoing court case relating to allegations of assaulting of an ex-girlfriend, which he has denied, was pushed to five sets but came away victorious 4-6, 6-1, 5-7, 7-6, 6-2