London: Novak Djokovic survived his first serious test of the ATP Tour Finals as the World No 1 advanced to the final with a 6-1, 3-6, 6-0 victory over Japan's Kei Nishikori on Saturday.
Djokovic had swept through the group stage at London's O2 Arena in imperious style, but he was pushed harder by Nishikori, who became the first player to take a set off him since October, before a strong finish secured the Serb's fourth appearance in the final of the prestigious season-ending event.
The 27-year-old has now won 31 successive indoor matches, including 14 at the Tour Finals, and his final opponent will be either six-time champion Roger Federer or Stan Wawrinka, who were to meet in an all-Swiss semi-final later on Saturday.
Djokovic, who has lifted the Tour Finals trophy three times, remains on course to become the first man to win the event three years in a row since Ivan Lendl in the 1980s.
"Kei was playing great and this has been the best season of his life but he made some crucial double faults in the third set," Djokovic said.
"I will watch the other semi-final. I'll get some popcorn and enjoy it from my bed." On Friday, Djokovic had guaranteed he will finish top of the year-end world rankings for the third time in four years 1 a fitting reward for another dominant year.