I can't take it!: Rafael Nadal after losing a point (AFP Photo/Oli SCARFF )

London (AFP) - Rafael Nadal believes it was an error to keep the Centre Court roof closed as he lost an epic Wimbledon semi-final to old rival Novak Djokovic on Saturday.

Nadal was defeated 6-4, 3-6, 7-6 (11/9), 3-6, 10-8 in the second longest semi-final ever played at the tournament, at 5 hours and 15 minutes.

It was a second day of epic drama at the All England Club after Kevin Anderson had needed 6 hours and 36 minutes to beat John Isner on Friday.

That set the record for the longest semi-final at the tournament and became the second longest Grand Slam singles match ever played.

It also meant that Djokovic and Nadal had been unable to finish their 52nd career clash on Friday night.

Their semi-final was started under the roof and finished under it on Saturday despite clear blue skies and temperatures hovering close to 30 degrees.

Asked if it was logical to have the roof closed, the world number one said: "No. But I will not talk more about this.

"If I talk about it, then you are going to write about this, and I don't want you to write about this today."

Nadal, the 2008 and 2010 champion, was playing in his first semi-final at the All England Club since 2011 when he finished runner-up to Djokovic.

He believes his semi-final should have been played before the Anderson-Isner match on Friday.

That semi-final only finished just before 8pm making it impossible for Nadal and Djokovic to finish before the 11pm curfew.

"It's true that the schedule was a little bit tight knowing that the first match was between two big servers," said the 32-year-old.

"Of course you can't predict that they play that long.

"But yeah, knowing that, maybe would be better if they play us first at 1:00, that's all."

Djokovic, the Wimbledon champion in 2011, 2014 and 2015, will be bidding for a 13th Grand Slam title when he faces Anderson on Sunday.

That match will be played with the roof open.

However, he said he was happy to see it shut on Saturday.

"There was a dialogue, yeah," said Djokovic after his 52nd career clash against Nadal.

"I was for the roof because we started to play, and I wanted to play in the same conditions.

"I didn't ask them (the organisers). I just expressed my opinion because they asked for my opinion. But as I understood, they already made a decision."