Djokovic saved that set point but Nadal earned another with a whipped forehand victor.
Discussing his upcoming final with Anderson, who came through a six-hour-and-36-minute slog with Isner on Friday, Djokovic joked: "Hopefully we can first of all play, hopefully we can get on the court!"
But Nadal, chasing an 18th Grand Slam crown and in his first Wimbledon semi-final since finishing runner-up to Djokovic in 2011, then saved five break points in the second set to level the contest.
Kevin Anderson and John Isner called for Grand Slam chiefs to introduce a cut-off point for final set marathons after their Wimbledon semi-final entered the record books as the second longest ever singles match at a major. With both players capable of enormous serves, the two just kept blasting the ball past each other, trading service and sides of the court as the rules dictated, but rarely ever competing in a compelling rally.
Isner won that best-of-three match 7-6, 6-1.
Anderson had break points at 7-7, 10-10 and 17-17 before finally earning the decisive break - drawing a massive roar from the crowd.
Anderson had a break point at 7-7 and at 10-10, but he missed the first one as Isner hit an ace and the second one as he mishit a backhand.
He also broke the record for most aces in a Wimbledon tournament. "I think I can keep doing damage here", the No. 9 seed was quoted as saying afterward on the ATP World Tour's Web site.
With Anderson serving for the final at 25-24, Isner handed his opponent two match points when a return sailed long.More news: Israel strikes Hamas military targets in retaliation for rocket attacks
Anderson, a 32-year-old South African, reached the U.S. Open final last year and pulled off a quarterfinal upset Wednesday of top-seeded Roger Federer, which went to 13-11 in the fifth set.
Having once again swapped breaks early on in the fourth set, Anderson broke Isner for the third time, and took the match into a decider on his fourth set point.
This time, there was to be no tiebreak as the final set at Wimbledon is traditionally decided by a difference of two games. It's been a roller-coaster for him in the last couple of rounds but he had a day off and that means a lot. "I really do. I think with the performances I've had, I deserve to be in the semifinals", he continued.
"At the same time, I'm through to the final. Wow".
Wimbledon doesn't use tiebreakers in the fifth set for men, or third set for women, so there's nothing to prevent a match from going on and on and on - and that's precisely what Isner and Anderson did, often thanks to one ho-hum hold after another.
It surpassed the previous longest Wimbledon semi-final, between Djokovic and Juan Martin del Potro in 2013, which lasted four hours and 44 minutes.
"I apologise if I'm not more excited right now, it's just coming through something like that leaves so many mixed emotions". Then he might stand half a chance of a first Grand Slam title on Sunday.
When Kevin was 12 years old, he used to compete against Spanish tennis star Rafael Nadal on the juniors circuit.