Novak Djokovic was once the sick-note Serb whose undoubted promise was at the mercy of a variety of frustrating aches, pains and assorted strains.

But with a fourth Wimbledon title and 13th Grand Slam crown secured on Sunday, there is little doubt that the 31-year-old is one of the sport’s greats.

His triumph over Kevin Anderson was even more remarkable as it came just a month after he threatened to skip the All England Club when a quarter-final loss at Roland Garros left him without a Major title since completing the career Grand Slam in Paris two years earlier.

His ranking was at its lowest in 12 years; his confidence in the dust.

Now, Djokovic has 13 Slam titles, just one behind Pete Sampras and four back from Rafael Nadal, who he defeated in a five-set, 5-hour 15-minute semi-final.

He may be still be seven shy of Roger Federer’s record of 20 Majors but he has time on his side – he is five years younger than the great Swiss.

“If you told me six months ago I would be in the Wimbledon final, I would take it right away,” said Djokovic, who started playing tennis when he was four before leaving for Germany when he was 12 to escape the NATO bombs ripping Belgrade apart.

The Serb’s ability to thrive amongst the greats has never been in doubt, but the size of his heart led to questions in his early days.

At Wimbledon in 2007, he retired with a back injury in the third set of his semi-final against Nadal.

He also quit at the 2006 and 2007 French Opens at the third round and quarter-final stages respectively, while at the 2009 Australian Open, where he was defending champion, he pulled out of his quarter-final with Andy Roddick citing heat exhaustion.

But at the 2012 Australian Open, nobody was questioning his courage anymore when he beat Nadal in the longest Grand Slam final of all time, a draining 5hr 53min masterpiece.

Djokovic captured the first of his 12 Majors in Melbourne in 2008, but it was three years before he added his second.

He dropped gluten from his diet, his lithe physique allowing him to chase down lost causes, transforming him into the rubber man of tennis.

Djokovic also refused to accept the dominance of Federer and Nadal, who were carving up Majors for fun.

After leading Serbia to a maiden Davis Cup in 2010, he raced through the first half of 2011, building up a 48-1 winning run.

Only a semi-final defeat at the French Open prevented him from becoming just the third man to capture a calendar Grand Slam.

Despite that, he still finished 2011 with a 70-6 win-loss record, a haul of 10 tournament victories and year-end number one for the first time.

People’s champion?

Back-to-back Australian Opens followed in 2012 and 2013, although the French Open remained frustratingly out of reach with three heart-breaking losses until his 2016 breakthrough.

In Paris that year, he became the first player to break through the $100 million barrier in prize money.

Djokovic has also not been afraid to innovate, bringing in Boris Becker as part of his coaching team for the start of the 2014 season.

He then became a vegetarian.

Off court, Djokovic married long-time girlfriend Jelena Ristic in July 2014. They have two children, a son Stefan and daughter Tara.

However, despite his achievements, Djokovic appears doomed never to be held in the same esteem as Federer and Nadal, the people’s champions.

There are those that see something a little more calculating in the Djokovic make-up, a player prone to affectation.

In the 2015 French Open semi-finals, he was castigated for taking an eight-minute medical time-out after dropping the third set against Andy Murray.

At Indian Wells in 2016, he was roundly criticised for his comments on equal prize money for women.

Even at Wimbledon this year, he criticised some Centre Court fans for lacking respect towards him while schedulers exiled him to Court Two for his third round match.