Roger Federer was powerless to resist a relentless Rafael Nadal as the reigning French Open champion triumphed 6-3 6-4 6-2 in their semi-final at Roland Garros on Friday.

But it was why Federer came back to clay.

After overcoming close friend Stan Wawrinka in a thoroughly entertaining four-set match on Court Suzanne-Lenglen on Tuesday, he stated his motivation to get back on the red dirt for the first time since 2015 was the chance to take on Nadal – a point he reiterated after the surprised Spaniard refused to believe the remarks when they were put to him in a news conference.

"For me to get to Rafa is not simple. It took five matches here for me to win to get there. That's why I'm very happy to play Rafa, because if you want to do or achieve something on the clay, inevitably, at some stage, you will go through Rafa, because he's that strong and he will be there," said Federer.

"I knew when I signed up for the clay that hopefully that's going to happen. If I would have had a different mindset to avoid him, then I should not have played the clay. I think that mindset helped me to play so well so far this tournament."

It was an insight into a truly astounding thought process, the kind that only someone with 20 major titles to their name could possess. Most professionals would be elated to taste glory at the French Open and let someone else do the difficult job of ousting the 'King of Clay', something that has happened just twice in his 94 matches at Roland Garros. But not Federer. He wanted it the hard way.

Beating Nadal on clay is the ultimate challenge, something made even more difficult by the fact he is left handed. No man in the Open Era has dominated on the surface to the extent of the world number three, whose 11 crowns in Barcelona, Monte Carlo and Paris are unparalleled.

It is something Federer knows all too well. He has lost all six of his meetings with Nadal at the French Open, four of them coming in successive years and three of them in the final.

Having sat out Roland Garros in 2016 following knee and back issues, Federer opted to skip the following two editions to focus on grass and hard courts. The Swiss realised after a five-set semi-final loss to Milos Raonic at that year's Wimbledon that his age meant he needed to change his approach to ensure he remained healthy enough to continue competing at the highest level.

But when your body is breaking down and your status as an all-time great is already secure, why continue? How do you remain motivated when you have spent 13 years at the top of the sport?

For Federer, it was his love of tennis and passion for the finer details that got him through. Titles were no longer what he sought. Instead, he focused on the minutiae. He delved into the intricacies of the game and found new challenges. 

"You improve a lot as a kid, as a junior, as a teenager, and then all of a sudden progress is slow. At one point you come to a place where you're trying to just get back to that good place time and time again," he said after easing past Leonardo Mayer in the fourth round.

"I guess that's what I have been seeking, chasing, for the last however many years. And as different players come, you realise you have to adjust a little bit, either with your serve, either you tinker with technology, with the racquet size or whatever string technology, and maybe take the ball earlier or later.

"Whatever you're trying to do, there's always going to be a plan behind it. But I think tennis is a great sport, it never gets boring, because every day plays different, every opponent plays different, every guy gives you different struggles. For that reason, I never got bored of the game.

"That I see as a motivation, and then of course it's easy to be motivated playing at this kind of a stadium with full crowds, giving a standing ovation at the end. I would admit I would be struggling on court whatever, 23, with impossible shades and no people watching, especially after living the big courts."

Speaking after his straight-sets defeat on Court Philippe-Chatrier, Federer admitted he does not think there is anyone who could help him prepare to face Nadal on clay.

But he should be applauded for his desire to take on the ultimate challenge.