Having battled through 59 encounters with Rafael Nadal over 16 years of epic rivalry, Novak Djokovic faces the Spanish legend's heir apparent Carlos Alcaraz at the French Open in a match laced with era-defining potential.
Djokovic will be playing a 45th Grand Slam semi-final on Friday; for Alcaraz, it will be just his second.
With Roger Federer retired and Nadal nursing a hip injury until next year, 36-year-old Djokovic has the responsibility of preserving the legacy of the 'Big Three'.
"It's definitely the biggest challenge for me," said Djokovic, chasing a third French Open title and men's record 23rd Slam which would break the tie he currently shares with Nadal.
Friday's showpiece will be the first time Djokovic and Alcaraz have met at a Grand Slam and only the second time in their careers.
Alcaraz, then still 19, defeated the Serb from a set down in the semi-finals of the Madrid Open last year, a day after he had knocked out Nadal on the faster, higher altitude courts of the Spanish capital.
Djokovic has 90 career wins at Roland Garros and is playing his 11th semi-final.
Meanwhile, two-time champion Iga Swiatek looks to reach a third French Open final in four years on Thursday while Aryna Sabalenka puts her 12-match Grand Slam winning run on the line in the Roland Garros semi-finals.
Swiatek is bidding to become the first woman to successfully defend the title in Paris since Justine Henin in 2007 after dispatching Coco Gauff in a rematch of last year's final.