Two forces of nature will collide on Sunday in the French Open final, and something will have to give.
It will be Rafael Nadal, the man who barely ever loses at Roland Garros, against Novak Djokovic, the man who only ever loses against himself.
And behind it all will be the over-arching contest to see who can one day claim to be the greatest player of all time. A win for Nadal puts him level with Roger Federer on twenty Grand Slam titles, while defeat would mean Djokovic climbing up to eighteen.
Novak Djokovic took a step closer to his 18th Grand Slam as he reached the French Open final
He faces a purring Rafael Nadal, a man who has never lost a final in 12 efforts at Roland Garros
Djokovic only made it after being given an almighty scare by Stefanos Tsitsipas, who saved a match point in the third set to force it the distance before losing 6-3 6-2 5-7 4-6 6-1 in three hours and 54 minutes.
It provided some of the best tennis seen all year before he ran out of legs towards the end against an opponent who stayed admirably unflustered in the face of a quality assault, which saw him broken three straight times in the middle of the match.
'I looked calm on the outside but I wasn't inside,' said Djokovic. 'Mentally I stayed there after the third set. Rafa is the favourite for the final, this is his house.'
How much the Greek has taken out of him remains to be seen.
Djokovic was given the more extensive semi-final workout in a five-set thriller on Friday night
The 34-year-old Spaniard is a master of bringing himself to the boil at just the right time in the Majors, and he looked like he was peaking perfectly in subduing the challenge of Diego Schwartzmann, beating him 6-3 6-3 7-6.
Equalling Federer is finally within sight for both men, and with the 39 year-old Swiss sitting out the season with injury Nadal has reached the final without having lost a set for the sixth time. Federer probably would have felt helpless anyway, as his days of hoping the win Paris are gone.
For Djokovic victory would represent the second time in his career when he has held all four Majors at once, but he denied this would be the