World number one Rafael Nadal called his long-time rival Novak Djokovic as "one of the more complex" players he's ever met. Nadal and Djokovic will clash for the 52nd time, with a Wimbledon final spot at stake.

Nadal, the 2008 and 2010 champion at the All England Club, trails Djokovic, the 2011, 2014 and 2015 winner, 26-25 in a rivalry which began at Roland Garros 12 years ago.

Along the way, they have fought out a series of classic and epic battles, including Djokovic's 5-7, 6-4, 6-2, 6-7 (5/7), 7-5 Australian Open final victory in 2012.

At five hours and 53 minutes, it was the longest final ever at a Grand Slam. The following year, Nadal downed the Serb - the World No 1 at the time - 6-4, 3-6, 6-1, 6-7, 9-7 in the semi-finals in Paris, this time in four hours and 37 minutes.

"It's always a big challenge to face Novak," said 32-year-old Nadal who is back in the semi-finals at Wimbledon for the first time since 2011 when he finished runner-up to Djokovic.

"He is one of the more complex players that I ever saw in our sport. You know that you can't win against him if you don't play very well." 

Nadal is chasing an 18th Grand Slam title, which would put him just two behind Roger Federer, who was sensationally knocked out in the quarter-finals by Kevin Anderson.

For his part, Djokovic is eyeing a 13th major after making the semi-finals of a Grand Slam for the first time since finishing runner-up at the 2016 US Open. This time last year, few would have expected to see either man back in the last-four at the All England Club.

Nadal was knocked out in the fourth round, losing 13-11 in the final set to Luxembourg journeyman Gilles Muller.

On four of his previous five visits to south-west London, he had been defeated by players outside the top 100.

Djokovic's 2017 Wimbledon campaign ended in a quarter-final retirement with an elbow injury which led to surgery and precipitated a worrying dip in form and confidence.

When he lost in the French Open quarter-finals to World No 72 Marco Cecchinato last month, he even suggested he was ready to skip Wimbledon this year as his ranking slipped to 22, his lowest since August 2006.

But the 31-year-old has been rejuvenated at Wimbledon, sweeping into the semi-finals for the eighth time.

With inputs from PTI