Andy Murray has already scaled the tennis summit but Japan’s Kei Nishikori did his best to loosen his footing before falling in a three-hour thriller at the ATP World Tour Finals on Wednesday. Home favourite Murray’s insatiable will power allowed him to prevail in a brutal encounter 6-7(9), 6-4, 6-4, keeping him on course for his first title at the year-ender.

Should he achieve that in his eighth attempt it would guarantee the 29-year-old end the year as world number one ahead of Novak Djokovic who would steal back the crown if he manages a fifth straight title at the O2 Arena. Misfiring Murray looked in trouble when Nishikori edged a 20-point tiebreak to win an 85-minute opening set. But he clawed his way back to claim a 21st consecutive victory in three hours and 20 minutes.

It avenged his five-set defeat at the hands of Nishikori in the US Open quarter-finals — from which he has since embarked on the run that snapped Djokovic’s 122-week hold on power. With two wins from two, Murray would have been assured a semi-final berth had Marin Cilic beaten Stan Wawrinka in the later group match but Wawrinka recovered from his drubbing by Nishikori to win 7-6(3), 7-6(3).

Murray will now face US Open champion Wawrinka on Friday knowing anything but a straight-sets defeat would suffice. Murray’s game was out of kilter throughout a first set in which Nishikori’s punchy groundstrokes led the Scot a merry dance. But he stubbornly kept his nose in front.