Andy Murray and Novak Djokovic, the dominant forces of men's tennis, will collide in a fitting climax to the season at the ATP World Tour Finals after taking vastly different paths to the title match.
Murray, who should trademark the 'tennis epic', spent three hours 38 minutes - a tournament record - quelling the ferocious firepower of Milos Raonic, dragging himself to a 5-7 7-6 (5) 7-6 (9) victory in a fever-pitch atmosphere in London.
The Scot, aiming to win a maiden Tour Finals crown and clinch the year-end world No.1 ranking for the first time, had barely finished his post-match news conference before Djokovic completed a 6-1 6-1 rout of Japanese Kei Nishikori.
Murray, who plunged into an ice bath after surviving his gruelling battle, including saving a match point, also spent three hours 20 minutes beating Nishikori on Wednesday.
Only he knows what is left in the tank for Sunday (Monday NZT) but he is protecting a three-month unbeaten run, a streak that helped eclipse Djokovic at the top of the rankings and now stands at a career best 23 wins, with fanatical zeal.
Djokovic will be the fresher man and, after a relatively lean second half of the year, would love to snatch back top-dog status with a fifth consecutive title in Murray's backyard.
For organisers of the flagship event it is the dream scenario. It is the first time the final match of the season will decide who is ranked No.1.
"This has never happened," said the Serb who has beaten Murray in five of their seven grand slam finals, including in Australia and France this year.
"I'm privileged to be part of history. This is one of the biggest matches we will ever play against each other."
Whatever lies in store it will struggle to surpass the adrenaline-fuelled drama provided by Murray and Raonic.
The Scot was outplayed at times by the powerful 25-year-old Canadian who, apart from a two-game dip that cost him control of the match in the second set, was relentless.
Raonic led by a set and a break, twice broke serve to stay alive in a gripping decider, then saw a match point come and go in the tiebreak as he, like everyone recently, found Murray an impossible riddle to solve.
Murray looked out on his feet at times but scratched and clawed his way to a 77th win of a remarkable year on his fourth match point when Raonic netted at 10-9 in a tense tiebreak.
"It wasn't just physically hard, it was mentally a tough match. It was pretty stressful," the Scot said.