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 mens Grand Slam title and will face third seed Alexander Zverev in the semi-finals on his 36th birthday on Friday. 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. "In the end it has been a very emotional night for me," AFP quoted Nadal as saying. "Im still playing for nights like today. "But its just a quarter-finals match? So I didnt 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. "I cant 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 its 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.