THE eternal conundrum of a tennis Grand Slam - whether a possible champion would rather breeze through the early rounds, barely breaking a sweat, or come through unscathed from an early challenge to fight another day.

Most pundits would have said Novak Djokovic, who up until last week’s win at Eastbourne had been considered to be drifting through the last 12 months of his tennis career needed the match practice and mental sharpening that comes from going toe-to-toe with a world number 47 such as Martin Klizan.

Sadly he was not given the option, as the Slovak retired when trailing 6-3 2-0 to the former world number one - citing a long-standing calf injury - and Djokovic goes through to face Czech Republic’s Adam Pavlasek in the second round.

The Serb then called for a new ATP Tour rule that allows players sustaining injuries having already entered a tournament to still receive their first round prize money should they withdraw before their match, to be rolled out into Grand Slams, too.

“I think the new rule that the ATP has reinforced allows players, who have made it to the Grand Slam main draw, to get what they deserve, but on the other hand allow someone else to play if they can. I support that kind of rule,” said the 12-time Grand Slam champion, whose match was followed by Alexandr Dolgopolov also retiring against Roger Federer.

“It doesn't happen often really. This tournament has a special place in players' careers. In this sport, there's so much weight behind it and significance about it.

“The aura of Wimbledon has probably always been the strongest of any other tournament. I'm sure that most of the players on the tour, if not all, feel that.

“Especially if you walk out on the Centre Court, there is a responsibility. I'm sure they tried their best, but it is what it is.”

Struggling for form since his shock third-round exit to Sam Querrey at last year’s Wimbledon, the man who had just won the 2016 French Open to hold all four Grand Slam titles at the same time, saw Andy Murray surpass him at the top of the rankings before the year was out.

Now down to fourth in the 12-month rankings, and sixth in the 2017 standings - although seeded second at SW19 thanks to his record on the grass courts of Wimbledon - Djokovic returned to The Championships with something to prove.

That remains the case after Klizan, struggling with his movement, failed to challenge the 30-year-old in a routine first set on Centre Court.

And when he came to the net having fallen 0-2 down in the second set, Djokovic’s passage to the second round was confirmed.

With both he and Murray enjoying a recent upturn in form having struggled to be at their best in 2017 and the old guard of Federer and Rafael Nadal enjoying Indian summer’s in their careers, the prospect of the fabled ‘big four’ slugging it out at Wimbledon once again now seems a distinct possibility.

Djokovic is seeded to meet seven-time Wimbledon champion Federer in the semi-finals, and he explained why the quartet had enjoyed such dominance at the event in the last 15 years - but warned that their reign will inevitably come to an end.

“The four of us have been aiming always to really peak in the biggest tournaments,” he said. “For some reason, we've been very successful in the last ten or plus years.

“Grand Slams, Roger had a record-breaking number of semi-finals in a row. I had also many in a row.

“Murray and Nadal have also been very consistent. It's a great era of men's tennis, no doubt. The four of us have produced a lot of great matches and rivalries.

“I think from one way it's good for the sport. On the other hand, you can't expect that it is going to last for a long time. Eventually there will be a different winner.”

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