Novak Djokovic has endured plenty of pain and disappointment in the last two years, but the former world No 1 secured a place in the Wimbledon semi-finals for the eighth time in his career here on Wednesday by beating Kei Nishikori 6-3, 3-6, 6-2, 6-2.

On Friday the 31-year-old Serb will renew his rivalry with Rafael Nadal, who won a titanic struggle against Juan Martin del Potro which lasted four hours and 47 minutes. Nadal, who was playing in his first quarter-final here for seven years, won 7-5, 6-7, 4-6, 6-4, 6-4 to stay on course to win the title here for a third time.

Djokovic, three times a champion at Wimbledon, played in his last Grand Slam semi-final nearly two years ago at the US Open. The 31-year-old Serb has struggled regularly ever since he completed his collection of Grand Slam titles by winning the French Open in 2016 and took off the last six months of last year because of a persistent elbow problem.

However, having elbow surgery appears to have solved his physical issues and his confidence is growing with every victory. Twelve months after retiring during his quarter-final here against Tomas Berdych because of the elbow injury, the 12-times Grand Slam champion underlined his upturn in form by beating Nishikori for the 13th time in a row. In Friday’s semi-finals he will meet the winner of Rafael Nadal’s heavyweight showdown with Juan Martin del Potro.

Once again Djokovic won after appearing to be fired by a sense of injustice. Against Kyle Edmund on the same Centre Court four days earlier he had been unhappy with the crowd, claiming spectators had tried to unsettle him by making noises as he served, but on this occasion he reserved his ire for Carlos Ramos, the umpire.

Ramos handed Djokovic a code violation for unsportsmanlike conduct after the Serb bounced his racket on the grass in frustration – damaging the court surface is regarded as one of the most heinous crimes in these parts – and another for taking too much time between points when serving. Djokovic later accused Ramos of “double standards” after claiming Nishikori had also thrown his racket but had gone unpunished.

“I thought it was unnecessary to get the warning,” Djokovic said after the match. “I didn’t harm the grass. I know how I threw the racket. He even threw his racket in the fourth set. The chair umpire said he didn’t see it, so I got the warning and he didn’t. I think it’s not fair, but it is the way it is. In the midst of the emotions in a tough match it happens.”

Nishikori reaches to return a forehand shot (Getty Images)

Nishikori, who was attempting to become the first Japanese player to reach the Wimbledon semi-finals for 85 years, made too many errors in the opening set, which Djokovic won after making the vital break of serve in the eighth game. The Serb continued to set the pace in the second set but failed to convert four break points in Nishikori’s first two service games.

His frustration was evident as he threw his racket on the grass, for which he was given the code violation, and his mood darkened further in the next game as Nishikori broke for a 3-1 lead.

After serving out for the second set, Nishikori had a chance to take a grip on the third when Djokovic went 0-40 down serving at 2-2, but the 12-times Grand Slam champion’s response was magnificent. Having fought back to hold serve, he then broke to lead 4-2, after which he punched the air in celebration and bellowed out a roar of “C’mon!”

Djokovic’s response appeared to knock the stuffing out of Nishikori, who suddenly started making more errors. Djokovic broke again to take the third set and then got the better of three breaks of serve in the first four games of the fourth. Even receiving his time violation at 4-2 did not knock Djokovic out of his stride.

The Serb looks back to his best (Getty Images)

In the open era only Roger Federer, Jimmy Connors and Boris Becker can better Djokovic’s tally of eight Wimbledon semi-finals. His total of 32 appearances in all Grand Slam semi-finals is bettered only by Federer, who has played in 43.

Djokovic will renew a rivalry which has seen him beat Nadal in 26 of their 51 matches. The Serb came out on top in their last meeting here in 2011, when he won the title for the first time by beating Nadal in four sets. Four years before that Djokovic retired hurt in the third set of their semi-final, which is their only other previous meeting at the All England Club.

Nadal, who chose not to play any warm-up tournaments before arriving here following his exertions in winning his 11th French Open last month, had not lost a set in his first four matches but was pushed to the limit by Del Potro in a quarter-final full of spectacular tennis.

Having lost the first set, Del Potro was in the driving seat after winning the next two, but Nadal levelled the match after breaking the world No 4 to love in the fifth game of the fourth set.

The match featured some spectacular rallies, particularly in the fifth set. With the court surface becoming slippery because of the evening dew, both men suffered falls.