From the years spent watching Rafael Nadal, I think we have all imbibed, at least on some level, the lesson that it takes a lot for him to lose a tennis match. Whether he be tired, injured, or simply in rotten form, Nadal is rarely ever beaten before he’s dead and buried beyond reasonable doubt. That feeling is amplified appreciably when clay and the best-of- five set format are introduced into the equation; Nadal, as the surface’s non-pareil, won’t drop three out of five sets on the dirt unless he’s been wholly outlasted, outfought and outclassed by a zoning foe. Only two men have managed the feat in the past: Robin Soderling and Novak Djokovic. On Friday, Argentina’s Juan Martin del Potro will attempt to become the third man to bring the king of clay down from his hegemonic perch at Roland Garros.

The enormity of Nadal’s dominance at the French Open is common tennis knowledge, so it provides little in the way of illumination to recapitulate that here. For a glance at the asymmetry between the respective histories of Nadal and del Potro at this tournament, consider that, from 2010 to the present year, del Potro has actually skipped the French Open half as many times as Nadal has won it overall. Although it’s obvious that Nadal has vastly more impressive clay court pedigree than del Potro, such a statement conveys little because he has achieved surpassingly more on the surface than pretty much any player one could care to mention.

It’s been nine years since del Potro contested a French Open semi-final—which is the furthest stage he has ever reached at Paris—and much has changed since then. Over the past nine years, the 29-year-old has experienced the peaks and troughs of what professional tennis has to offer (and everything in between), while having to creatively redevelop his style of play in order to reclaim the place he occupied in the ATP ecosystem all those years ago.

After his most recent return from injury, del Potro has faced Nadal twice, coming out on top in a memorable three-set semi-final clash at the 2016 Rio Olympics before losing to the Spaniard in four sets at the 2017 US Open. On the evidence of those two contests alone, matches between the pair are finely poised when they play on slow, high bouncing hardcourts. The question most pertinent to the upcoming semi-final is how does this matchup resolve itself on clay?

There isn’t a lot to go by to answer this question. Nadal and del Potro have played two clay court matches against each other, both of which Nadal won. Nadal beat del Potro easily in the first round of the 2007 French Open, and won over him again in the 2011 Davis Cup final, on that occasion dropping the opening set. During Friday’s match, Nadal, as he is adept at doing on any terrain, will loop topspin-loaded forehands to del Potro’s functional backhand; del Potro will be able to get decent depth on his reply most of the time, but when he doesn’t, the outcome of the rally will no longer be on his racket. If this pattern regularly unfolds, then del Potro will be engaged in an uphill struggle just to stay in the longer exchanges, let alone win them. In addition, del Potro must remain alert to the effectiveness of Nadal’s down-the-line forehand, which the latter can unleash even when off-balance or positioned a good distance behind the baseline, as well as his cross-court backhand, which he has been hitting with authority when he gets the chance to step into the court and rip it.

Of course, it is not as if del Potro does not have weapons of his own to hurt Nadal with. He possesses a precise and powerful forehand, which, when he hits it from his backhand corner, can open up the court and force his opponent to give up vital yards behind the baseline. Del Potro’s 6’6″ height and enormous wingspan also allow him to be more comfortable than most handling Nadal’s high-bouncing topspin, which is a plus, especially on clay. His chances of pulling off the upset rise by a good margin if he manages to control the center of the court, pin Nadal behind the baseline, and avoid getting dragged into drawn-out cross-court rallies, of which there will only be one winner.

If Nadal gets off to as slow a start against del Potro as he did in his previous two matches, then he will have his work cut out for him in the early stages at the very least. On this point, Nadal does not look nearly as imperious at this year’s French Open as he did 12 months ago, when it was beyond anyone to take more than four games off him in a set. Last week, free-swinging journeyman Simone Bolelli took Nadal to a tiebreak and very nearly won it. Unheralded youngster Maximilian Marterer pushed Nadal hard in the third set of their encounter. In the quarter-final, del Potro’s compatriot, the diminutive and indefatigable scrapper Diego Schwartzman, stole one set and threatened briefly to nab another.

These hiccups can be explained to an extent. The argument goes, according to some, that Nadal on clay when it rains is not the same Nadal on clay when it doesn’t because humid, dry conditions ensure that his topspin groundstrokes explode off the court and bounce further away from his opponent’s strike zone. Conversely, the ball does not bounce  advantageously high in cool, damp conditions, which neuters his default strategy somewhat. We can all acknowledge that there is a kernel of truth to this observation, but come rain or come shine, only a flawless performance from del Potro will prevent Nadal from getting to an eleventh French Open final.