Roger Federer will take on his old rival Rafael Nadal for the 39th time on Friday after reaching the French Open semi-finals for the first time in seven years.
Having returned to the tournament after a four-year hiatus, Federer has produced some vintage form on the clay and he was superb in a 7-6 (4) 4-6 7-5 (5) 6-4 victory over countryman Stan Wawrinka.
Wawrinka had beaten Federer in straight sets in the quarter-finals here four years ago but is no spring chicken himself at 34 and had a five-hour match against Stefanos Tsitsipas on Sunday in his legs.
Nevertheless, Wawrinka, the champion in 2015, roused himself to take the second set and both men had chances in the third.
It was Federer, though, who took it on a tie-break and a break of serve in the ninth game of the fourth set set up the 37-year-old to book his place in the last four.
There was a brief wobble, with Federer perhaps feeling the significance of the occasion, but he put away a volley on his third match point to clinch victory after three hours and 35 minutes.
Nadal's match was much more comfortable, the second seed easing into a 12th semi-final here with a brutal 6-1 6-1 6-3 victory over seventh seed Kei Nishikori.
Nishikori had been pushed to five sets in his previous two matches and could find nothing to hurt Nadal, who will now look to maintain his record of never having lost at Roland Garros once he has reached the last four.
The only thing that held him up was a brief thunderstorm in the third set. Nadal looked decidedly unhappy to be instructed to leave the court at 4-2 but wasted little time wrapping things up on the resumption.
Nadal leads his head-to-head against Federer 23-15 and has won all five of their matches at Roland Garros, most recently in four sets in the final in 2011.
But Federer has had the better of their recent meetings, winning the last five, including a memorable five-set victory in the 2017 Australian Open final.