LONDON: 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 semi-finalist 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 semi-final 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 following a COVID-19 standoff and then losing to old adversary Rafa Nadal in the quarter-finals of the French Open.

He might even be barred from the U.S. Open over his decision to shun a COVID 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."

DJOKOVIC ONSLAUGHT

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.

Sinner began his third Grand Slam quarter-final anxiously, losing the first seven points and then trailing 4-1.

But he then produced an astonishing level of tennis to give the world number three the run-around.

He sent a forehand whistling past an outstretched Djokovic to break serve at 5-5 and took the opener after a drop shot gave him a second set point.

Oozing confidence, Sinner dominated the second set as Djokovic seemed at a loss about how to keep the Italian at bay.

The Serbian's team, including wife Jelena and former Wimbledon champion Goran Ivanisevic, looked pensive.

But they need not have worried as, after Djokovic's face-to-face in the mirror, their man came back in defiant mood.

A superb volley helped him break serve for a 3-1 lead in the third set and after shovelling up a drop shot to win a point at 30-30 in the next game, Djokovic conducted the fans' cheers.

Two Sinner double faults in the first game of the fourth set were a gift for Djokovic who raced into a 4-0 lead.

Sinner clenched his fist when he held serve at the start of the decider but Djokovic was relentless and once he got his nose in front he was unstoppable.