Just when Novak Djokovic's troubling year looked like hitting another low he salvaged his bid for a fourth successive Wimbledon title by coming back from two sets down to beat Italian Jannik Sinner in the last eight on Tuesday.

The Serbian top seed had looked in all kinds of trouble against the inspired 20-year-old after being outplayed for two sets but stormed back to win 5-7 2-6 6-3 6-2 6-2 and set up a clash with Britain's surprise semifinalist Cameron Norrie.

In the end there was an air of inevitability about the outcome as the battle-hardened 35-year-old seized control to reach his 43rd Grand Slam semifinal and 11th at Wimbledon. He also extended an unbeaten run at Wimbledon that goes back to 2017 and now stands at 26 matches.

Djokovic has not added to his 20 major titles this year after being deported before the Australian Open after a Covid-19 standoff and then losing to old adversary Rafa Nadal in the quarterfinals of the French Open. He might even be barred from the US Open over his decision to shun a Covid-19 vaccine but kept alive the prospect of facing Spaniard Nadal in Sunday's Wimbledon final with a seventh career comeback from two sets down.

After taking the acclaim of the crowd on Centre Court, Djokovic explained how he had turned it around.

“The first two sets compared to the last three was like two different matches,” Djokovic, who is now joint second all-time with Jimmy Connors on 83 Wimbledon match wins, said.

“He [Sinner] was the better player for two sets, then I went out and had a toilet break and had a little pep talk with myself in the mirror, it's actually true.

“I broke early in the third set and that gave me a confidence boost and I saw a little doubt in him.”

Sinner, the 10th seed, looked primed for the biggest win of his career to follow in the footsteps of compatriot Matteo Berrettini who reached last year's showpiece match. But he wilted under a Djokovic onslaught.

When Djokovic produced a miraculous winner on the slide to earn a break point for a double break in the seventh game of the fifth set, ending up on his belly in a superman pose, Sinner knew he was facing mission impossible.

The Italian belted a volley long on the next point and then Djokovic held to love to seal victory.

Ninth-seed Norrie reached his first Grand Slam semifinal when he twice came from behind to beat unseeded Belgian David Goffin in five sets on Tuesday to set up a dream meeting with Djokovic.

Norrie looked out of sorts for much of the match but, lifted by the fans who threw their support behind their adopted SA-born home hope, found an extra gear in a tense fifth set to secure the biggest win of his career by 3-6 7-5 2-6 6-3 7-5.

“I can't even talk, I'm so happy to get through with such a great team, such a great family and friends here,” said the 26-year-old who was ranked 50th a little over a year ago.

“It wasn't going my way from the beginning. All credit to David, he was moving me and playing really good, but thanks to you guys [the crowd] I managed to stay as patient as I could.

“It was all just adrenaline, using my legs and trying to put the ball in the court, and it's great to get over the line.”