On the penultimate point of Friday's semi-final, Rafael Nadal worked the weary but willing figure of Juan Martin del Potro left and right like the shuttle on a loom.
Eventually del Potro threw up a hopeful lob, kept on running, and buried his head in the courtside flower-bed. It is testament to his enduring good humour that he still had a rueful grin on his face.
The first set of this semi-final had been competitive, especially when del Potro brought up three break points on the Nadal serve at 4-4. Yet once Nadal had staved off those threats with some breathtaking tennis, and then played an even better game to clinch the set, the defiance drained from del Potro's dispirited frame.
It didn't help that he had suffered a recurrence of his groin injury early in the match, which caused him to order some anti-inflammatory medication at the second changeover. In the end, though, Nadal lived up to his reputation. And when you have won 85 of 87 matches at a particular tournament, that is not an easy thing to do.
"I think that was my chance of the match," said del Potro, in reference to his first-set opportunity. "I had a lot of break points. I couldn't make it. And when you don't take your chances against the No 1 in the world, you're in trouble.
"Rafa served well, played good points in that break points, and I got unlucky in that moment," added del Potro, who won only seven games in this 6-4, 6-1, 6-2 towelling. "Could be different match if I win the first set. But then he made me run a lot. Intensity is too high the whole match, and I couldn't stay there after the first set."
It has been the same story all fortnight. Once Nadal has moved ahead, he has gained in confidence, and moved into the kind of overdrive that no player on earth can match. At least, not on their current form.
Perhaps Novak Djokovic could have stood his ground, at the peak level that brought him four straight majors a couple of years ago. He is the one person who has forced Nadal to change his tactics, by going after the high-kicking ball with his peerless backhand.
If you can't do that – and no-one else has Djokovic's timing or flawless mechanics – your best chance is to apply pressure early, and hope to disconcert Nadal in the way that Diego Schwartzman did in heavy, damp conditions on Wednesday night.
The upshot of that extraordinary passage of play was that Nadal lost a set at Roland Garros for the first time since Djokovic beat him in 2015. He has since admitted that he was "lucky" to be reprieved by the rain, which grew heavy enough to force the players off while Schwartzman was leading by a set and a break.
There are few positive omens for Dominic Thiem, the 24-year-old Austrian who beat Marco Cecchinato comfortably – 7-5, 7-6, 6-1 – in the other semi-final. But at least the forecast suggests that conditions will be wet and heavy again on Sunday, which might take some of the pop off Nadal's vicious top-spin and give Thiem more time to wind up his own piledrivers.
It is hard to avoid the feeling that Nadal has come through his one dodgy moment of this tournament, and that he survived it with a little help from above. This year, the King of Clay is ruling by divine right.
But if Nadal's hegemony is to be tested, Thiem is the right man to do it. He is surely the second-best clay-courter in the world, having inflicted Nadal's two most recent defeats on this surface. And his attitude on Friday in the interview room showed the right mixture of realism and self-confidence.
"If I want to beat him, I have to play like I did in Rome and in Madrid," said Thiem, in reference to his two most recent successes over Nadal. "I'm also aware that here it's tougher. He likes the conditions more here than in Madrid, for sure, and best of five is also different story.
"Of course there is pressure, because I went a very long way now and I don't want to lose the finals. But I think if I'm facing Rafa, I'm not the one who has the pressure."
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