Novak Djokovic clawed his way to a two sets to one lead over great rival Rafael Nadal under the Centre Court roof before their scintillating Wimbledon semi-final was paused with the contest balanced on a knife-edge on Friday.With the clock slipping past 11pm -- the official curfew time for action at the All England Club to end for the day -- Djokovic survived three set points in a gripping tiebreak before outlasting Nadal in a 17-stroke rally to edge ahead in the match.READ | 6 hours, 36 minutes! Kevin Anderson downs John Isner in epic Wimbledon semi-finalBattle will resume at 1200GMT on Saturday with the Serbian three-time champion 6-4, 3-6, 7-6(9) ahead and needing one more set to book a Sunday showdown with South African Kevin Anderson.<iframe width=”560” height=”315” src=”https://www.youtube.com/embed/oYVMqLUXK20?ecver=1” frameborder=”0” allow=”autoplay; encrypted-media” allowfullscreen></iframe>The eighth seed earlier won the longest-ever Wimbledon semi-final in a test of endurance with American John Isner that finished 26-24 in the fifth set after six hours and 36 minutes.Following a three-year wait for Djokovic and Nadal to continue their Grand Slam rivalry and then an afternoon caged in the locker room while the Anderson and Isner marathon unfolded, they were finally let loose at gone 8pm with the roof closed.READ | Serena Williams seeks eighth Wimbledon crown to cap another comebackWith David Attenborough, the doyen of countless BBC nature documentaries, a guest in the Royal Box, the two players tore into each other from the start like hungry lions.Nearly three punishing hours later they both left Centre Court with their title hopes still intact.The exhausted Anderson can only hope that another two sets of equal ferocity are required on Saturday. Then he might stand half a chance of a first Grand Slam title on Sunday.PROLIFIC RIVALRYDjokovic and Nadal had met 51 times before Saturday’s semi-final -- the most prolific rivalry in men’s tennis.READ | ‘It’s crazy’: Serena Williams shocked after reaching 10th Wimbledon finalBut they had not shared a Grand Slam stage since Djokovic inflicted a bitter defeat on Nadal at Roland Garros in 2015.The 31-year-old Serb, who leads their head-to-head series 26-25 but trails 12-17 in Grand Slam titles, has been in the doldrums for a year but in the past fortnight has rekindled the inner fire that once enabled him to barge Roger Federer and Nadal aside at the top of men’s tennis.There was no easing into Saturday’s 15th Grand Slam meeting between the pair. It was full tilt from the first point.When the opening three games lasted 16 minutes it was clear the three-hour window to finish the match was insufficient.Striking the ball clean and true, Djokovic pressurised Nadal and broke in the seventh game when the Spaniard netted a forehand. Djokovic sealed a sensational first set in 47 minutes.READ | Serena Williams sets up Wimbledon final clash against Angelique KerberSecond seed Nadal saved a break point at the start of the second set and celebrated holding serve with a trademark upper-cut fist pump.With Djokovic hitting the lines with relentless regularity, Nadal saved two more break points at 1-1 then seized the initiative to punish Djokovic for his first lapse.The 12th-seeded Serb broke back immediately with a dipping forehand but Nadal replied with another break which proved decisive as he levelled the match.If anything the quality went up another notch under the lights in a third set that went with serve to the tiebreak.Djokovic led 5-3 but Nadal won a 23-stroke exchange with a dropshot to lead 6-5. Djokovic saved that set point but Nadal earned another with a whipped forehand winner.Again Djokovic resisted, and again at 8-7 down. Nadal saved one set point himself but Djokovic earned one more and forced an error after another long rally to grab the overnight lead.