Roger Federer finally got himself into a dogfight at this French Open after a relatively quiet run to the quarter-finals, where he survived an all-Swiss scrap with his long-time friend and rival Stan Wawrinka on Tuesday afternoon. Victory, though, has delivered him an even tougher assignment, the ultimate test on clay: a semi-final against the surface’s finest exponent, Rafael Nadal, their 39th career encounter.

The defending champion Nadal had a far easier time of it against Kei Nishikori – winning 6-1, 6-1, 6-3 in under two hours – than Federer did in seeing off the stubborn muscularity of Wawrinka, 7-6 (4), 4-6, 7-6 (5), 6-4 in three hours and 35 minutes.

The tie-breaks could have gone either way, as Wawrinka played with the sort of fierce energy and power of which few players are capable, but Federer, husbanding his resources, had enough energy and nous to win for the 23rd time against him in 26 matches.

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Nadal is still favourite to win a 12th title here, slightly ahead of the world No 1 Novak Djokovic, who plays Alexander Zverev in the second match on Court Philippe Chatrier on Wednesday, with Dominic Thiem and Karen Khachanov also on second, on Court Suzanne Lenglen. There is consensus the Serb is the only player left in the draw capable of stopping a rampant Nadal – and that is what the Spaniard has been for most of the tournament.

On day 10, he was as brilliant as he was on day one, when he beat the German qualifier Yannick Hanfmann – followed by another German qualifier called Yannick: Maden. David Goffin was his first genuine threat, and the Belgian became the only opponent to take a set off him so far. Nishikori, seeded seventh, was made to look second rate as Nadal made him suffer in the sultry, windy conditions.

As Nishikori said later : “I played too many hours on court the past week. Today, Rafa didn’t let me play how I wanted to play. If I’m not fresh, it’s not easy to stay with him. He hit very heavy, and he was serving well. He made me play every point. Even to get one game, it felt like very long. Credit to him, playing great tennis this week.”

Nishikori, who nearly beat Nadal on the clay of Madrid a few years ago before his body let him down, had the trainer on at the start of the third set, having won only two games in the first two. There are uphill battles and there is trailing Nadal at Roland Garros with a sore right shoulder.

Nadal said later: “I have been playing well, very solid. Winning good matches against tough opponents like today. I am happy with that.” He added: “Of course having Roger in the semi-finals is an extra thing. We shared the most important moments of our careers together. It is another episode. I am happy for that and excited, no? Will be a special moment. Let’s try to be ready for it.”

Federer and Wawrinka went at it from the first ball to the last in a thrilling encounter, full of rich strokes and no little emotion. Wawrinka had by far the more exhausting route to the quarter-finals but was not complaining.

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“I played really good from the beginning of the tournament,” he said. “I won some big matches, especially against Cristian Garín, played super well against Grigor Dimitrov. Then there were tough matches in two days followed by Stefanos Tsitsipas, who is really confident and playing well this year. But I was ready physically after all that time on the court. Today, to give another big battle against Roger was a tough one for sure. But I think in general it was a good battle, a great battle.”

In the pivotal third set, Federer had to battle through five deuce points in the 11th game to keep Wawrinka at bay and retain the lead on serve, but he could not avoid a second tie-break. Again he prevailed, but not before Wawrinka saved one of three set points with an ace.

Serving for the match at 5-4 in the fourth set, Federer double-faulted on his second match point but made sure of his concluding volley, and they embraced at the net with genuine warmth. Whatever their occasional differences in the past, they remain close friends and grand representatives of one of the sport’s smallest countries.

Federer said later that Andy Murray might have hinted at a premature “emotional” exit from the game when he lost in the first round of the Australian Open, before returning to London for a second hip operation. He welcomes Murray’s comeback, in doubles at Queen’s later this month but revealed “when I saw him in the locker after his match against [Roberto] Bautista Agut [in Melbourne in January], I was, like: ‘So what’s up? Are you really retiring?’

“He didn’t know. I was, like: ‘OK, clearly, there is misunderstandings or he’s not sure yet.’ I think it was just an emotional moment, And I think he was at a breaking point where he realised: ‘I cannot keep playing any more.’ I have been there. Like at Wimbledon, for instance, that year in 2016, I realised I cannot keep doing what I’m doing like this. It’s just not healthy any more.”

Except he did. And on Thursday he will play in his eighth semi-final at the French Open. It, too, might be his last match here.