The toughest thing to do in tennis is to win the calendar Grand Slam, of course, so if you wanted to be really nitpicky about this conversation, fine — what’s about to be said is not 100 percent accurate.

However, for all intents and purposes, the toughest thing to do in men’s tennis over the past 10 years has been to beat Rafael Nadal Parera at Roland Garros, the citadel in which he’d lost only one of his previous 71 matches on the terre battue of Paris.

On a gray day in the late spring of 2009, Robin Soderling did the unthinkable: Nadal had advanced through 31 rounds on Parisian clay without a blip, but Soderling put a “1” in Rafa’s loss column. Since that one slip, Nadal advanced through 39 more rounds at the French Open without interruption. Rollin’ at Roland — it’s been the most automatic thing in tennis for a full decade, save for a single, solitary afternoon against a Swede who wasn’t joking that day.

Now, finally, another person has beaten Rafa: The Djoker.

Novak Djokovic has demonstrated many times over that he can not only beat Rafael Nadal on clay, but utterly flummox the nine-time French Open champion. Djokovic can defend as well as Rafa. He can neutralize Rafa’s topspin crosscourt forehand with his crisp and dependable two-handed backhand. His return of serve can establish enough depth that Nadal can’t feast on short balls with his forehand. These and other ingredients — very much including a determination and will that can compare with Rafa’s fighting capabilities — have lifted Nole past Rafa on Roman clay… and the clay of Monte Carlo… but never before in Paris.

Six times, Djokovic and Nadal met on red brick — three of them were from 2006 through 2008, when Djokovic was just learning how to compete, and a wise-beyond-his-years Nadal was fully in his element. In 2012 through 2014, though, Djokovic had arrived as a full-fledged force in his sport. His 2011 season will always remain one of the greatest in the history of tennis. He bested Nadal in that 5-hour, 53-minute marathon in the 2012 Australian Open final.

In 2013, he broke Nadal’s stranglehold on Monte Carlo. In 2014 — and not for the first time — he defeated Nadal in Rome. Paris, though, demands best-of-five tennis, the attritional context in which Nadal’s physical and mental stamina have always made him tough to crack. Soderling’s huge and unrelenting hitting produced one of the all-time upsets in tennis, but on 70 other occasions, six against Djokovic and five against Roger Federer, Nadal stood supreme.

This is where the beginning of our story comes back into play.

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In 2006 and 2007, Federer would have pulled off the calendar Grand Slam had it not been for Nadal rising up and defending his (red-clay) turf at Roland Garros. In 2012, Djokovic came to Paris intent on achieving the calendar Slam, but a loss to Nadal in the final set him back, denting his confidence in ways that hijacked the rest of that particular year. Ever since Djokovic’s huge 2011 season, the drumbeat of “Djokovic’s gonna get him this time!” has grown louder, but in each of the past three years — with a new and improved Djokovic following his career metamorphosis in late 2010 and throughout 2011 — Nadal’s citadel in Paris was still strong enough to thwart Djokovic’s advances.

Forget the calendar Grand Slam, ye men of the ATP Tour: If you want to pull off the toughest feat in tennis, you have to go through Rafa at Roland Garros. The two feats are essentially one and the same, even though one requires more work to be done at Wimbledon and the U.S. Open… and, let’s not forget… a semifinal match on Friday plus a final showdown on Sunday in the City of Light.

The task for Novak Djokovic on Wednesday afternoon, then — in one of the most consequential quarterfinal matches ever staged in modern men’s tennis — was not a tactical one. It was not about finding a chess-match solution or a clever change in approach. Djokovic — by far the best player in men’s tennis right now, many thousands of rankings points ahead of No. 2 Roger Federer for the top spot in the sport — simply had to win the battle in his own mind.

In 2012 and 2014, Djokovic double-faulted on match point at the end of erratic performances. In the 2013 semifinal at Roland Garros, a failure to avoid touching the net at a crucial juncture in the fifth set caused Djokovic to lose a point… and his focus. Nadal is the greatest claycourt player who has ever lived because — on the surface which requires more stamina and more patience than any other — he makes opponents feel every ounce of his presence. Nadal conveys to claycourt opponents the realization that they’re going to have to hit four, six, nine, twelve extra high-quality shots to win single points. The awareness of the difficulty of the task becomes more oppressive for Nadal opponents than the task itself.

Djokovic is the one player whose defense and overall skill set were always good enough to cope with Nadal, but in the best-of-five cauldron, Djokovic’s concentration — one of his strongest attributes in pressure situations over the last five years — abandoned him.

Wednesday, Djokovic had to keep his eyes on the prize whenever Nadal pushed him.

That is exactly what the World No. 1 managed to do, and that is why The Citadel is now 70 and 2.

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There were two stages in this match — both near the ends of sets — when Novak Djokovic could have allowed inner doubt and past losses to Nadal on Court Philippe Chatrier to overwhelm his mind.

The first moment came after Nadal, serving at 5-6 in the first set, saved set point with an overhead that clipped the tape and stayed in the court for a winner. Djokovic could have allowed that bit of Nadalian luck to frustrate him. The 2012 version of Nole probably would have buckled.

The 2015 version calmly regrouped and won a pair of points to take the set, 7-5.

Late in set two, serving at 5-3 and deuce, Djokovic showed why this year was going to be different from past ones against the King of Clay. An absolutely ridiculous backhand volley pick-up, deftly redirected crosscourt to the ad-side service box, halted a Nadal rally in its tracks. Djokovic served out the set on the following point, and he had become the first person ever (not even Soderling did this in 2009) to take a two-set lead over Rafa at Roland Garros.

Those two moments in each of the first two sets showed that, at last, Novak Djokovic had found the composure needed to trust his talent and let his tennis — not his mouth — do the talking against the sport’s greatest claycourt champion.

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Djokovic’s decision to hire Boris Becker as his coach over a year ago was met with inconsistent results at the beginning (especially a quarterfinal loss to Stan Wawrinka at the 2014 Australian Open). In the present moment, though, Becker’s presence in Nole’s box is paying off, giving Djokovic that champion’s resilience Becker was known for in his career. Becker didn’t reinvent the wheel for Nole, much as Ivan Lendl didn’t overhaul Andy Murray’s style of play when he started coaching the Scotsman a few years ago. Players sometimes don’t need X-and-O coaching as much as they want to hear familiar words and encouragement from specific individuals, such that they feel they can act on those words. When you hear Boris Becker talk about mental toughness, you’re more inclined to take it to heart, even though dozens of other coaches might say the same thing in a similar context.

This match on Wednesday against Nadal was mostly between Djokovic’s ears. The straight-set result tells you all you need to know about the holistic — and to use a make-believe word, tennistic — condition of Novak Djokovic’s game.

The 2015 French Open is hardly over. Two more battles obviously await.

Yet, there is no question that Novak Djokovic has the table set, the feast laid out before him. Two more composed performances against players not named Nadal will give the world’s best tennis player a banquet of riches to cherish for the rest of his life.