Rafael Nadal insisted he still has work to do to win a 14th French Open despite knocking out Novak Djokovic and said it was "too late" to be playing after their quarter-final ended in the early hours of Wednesday.

The Spaniard is still on track for a record-extending 22nd men's Grand Slam title and will face third seed Alexander Zverev in the semi-finals on his 36th birthday on Friday.

"Playing another semi-finals here in Roland Garros means a lot to me."

— Rafael Nadal, 13-time French Open champion

Nadal took his head-to-head against defending champion Djokovic at Roland Garros to 8-2 with a 6-2, 4-6, 6-2, 7-6 (7/4) win which finished after 1:00 am local time.

Nadal hits a forehand against Djokovic at the Court Philippe-Chatrier in Paris on June 1. Photo: AFP

"In the end it has been a very emotional night for me," said Nadal. "I'm still playing for nights like today.

"But it's just a quarter-finals match? So I didn't win anything. I just give myself a chance to be back on court in two days. Playing another semi-finals here in Roland Garros means a lot to me."

The match ended in cool conditions under the Court Philippe Chatrier lights, with many fans covering themselves in blankets as the match stretched from May into June.

"It is too late, without a doubt," said Nadal who had asked not to play in the night session.

A supporter holds a flag with the colors of Spain during the match. Photo: AFP

"I can't complain because we have two days off now, but if you only have one day off, or like Zverev had in Madrid, when he had to play the final the next day, then it's a big issue.

"I understand the other part of the business, without a doubt, that television pays a lot of money...

"We need to find a balance."

Nadal, who won the Australian Open earlier this year, has struggled in recent weeks with a chronic foot injury.

He said before his match with Djokovic that it could potentially be his last on the Paris clay.

"I don't know what can happen," he admitted. "As I said before, I'm gonna be playing this tournament because we are doing the things to be ready to play this tournament, but I don't know what's gonna happen after here.

"I have what I have there in the foot, so if we are not able to find an improvement or a small solution for that, then it's becoming super difficult for me.

"So that's it. I am just enjoying every day that I have the chance to be here, and without thinking much about what can happen in the future."

Nadal will move two clear of Djokovic and Roger Federer on the all-time list of most men's major titles if he lifts the trophy again on Sunday.

But he played down the importance of the battle between the 'big three'.

"From my perspective it doesn't matter that much. We achieved our dreams. We make history in this sport because we did things that didn't happen before."