Should four-times defending champion Djokovic defeat Kei Nishikori in the day's second semi-final, Murray and Djokovic will face off on Sunday.
World number one Andy Murray survived his second marathon of the week to beat Milos Raonic 5-7 7-6(5) 7-6(9) in a nerve-jangling semi-final thriller at the ATP World Tour Finals on Saturday.
Outplayed at times by the big-serving 25-year-old Canadian who had a match point at the death, Britain's Murray scrapped and clawed his way to a career-record 23rd consecutive win in three hours and 38 minutes of spellbinding combat.
Should four-times defending champion Novak Djokovic defeat Kei Nishikori in the day's second semi-final, Murray and Djokovic will face off on Sunday with the title and the end-of-season world number one ranking on the line.
Murray's hold on the top spot he wrestled off Djokovic this month seemed to be loosening when an inspired Raonic took the opening set and broke early in the second.
But Murray, who had lost his three previous semi-finals at the year-ending tournament, regained his rhythm just in time to storm back in a fever-pitch atmosphere.
Raonic came within two points of victory at 5-5 in the second set tiebreak and kept his nose ahead in the decider until an exhausted-looking Murray pounced to break at 4-4.
Twice Murray served for the match, at 5-4 and 6-5, but Raonic showed incredible resolve to break and force a tiebreak. Going into the breaker the points score was 127-127 and defeat would have been cruel on either player. Murray had a match point at 5-6 but Raonic saved that with a blistering forehand. Raonic gave him another one when he drifted a backhand long but Murray sent a backhand over the baseline.
An ace brought up a third chance and again Raonic survived with a nerveless volley. Next it was Raonic's turn to have a match point, at 8-9, but Murray tucked away a winning volley.
A swinging wide serve gave Murray a fourth match point and Raonic finally succumbed as he has done six times against Murray this year, including in the Wimbledon final.
The match lasted 18 minutes longer than Murray's group stage win over Nishikori on Wednesday which set a new record for the longest three-set clash in the tournament's history. (Editing by Ed Osmond)
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