Paris - Novak Djokovic, fighting to extend his run as world number one, recovered from an early wobble to defeat Grigor Dimitrov in the last 16 of the Paris Masters on Thursday.
The record four-time champion will remain above the in-form Andy Murray at the top of the rankings if he reaches the final in the French capital, but Djokovic was made to sweat before claiming a 4-6, 6-2, 6-3 victory.
He fell behind after losing serve twice in succession in an hour-long first set and then required medical treatment on his right knee after landing awkwardly while stretching for a return.
But Djokovic kept his calm as the errors mounted from Dimitrov to claim the second set with relative ease, and he broke early in the decider to wrest away control of the match.
The top seed next takes on Marin Cilic, who earlier punched his ticket to the Tour finals in London with a 6-3, 7/6 (11/9) defeat of David Goffin
Murray faces French 13th seed Lucas Pouille later as the Briton continues his assault on Djokovic's number one ranking.
The three-time major champion can supplant his long-time rival at the summit by lifting a maiden Paris title should Djokovic fail to reach the final.
However, if Cilic beats Djokovic in the quarter-finals on Friday then Murray making it to Sunday's final would be enough to propel the Scot to the top of the pile.
Cilic claimed the penultimate spot in the eight-man field for the prestigious November 13-20 event in London after seeing off Goffin on his sixth match point.
"That was the goal of the season for me, to reach the Tour finals in London," said Cilic, who eliminated Goffin from contention in the process.
Fourth seed Milos Raonic shook off a slow start against Uruguay's Pablo Cuevas to advance 4-6, 6-1, 6-2 and set up a quarter-final showdown with Kei Nishikori or 2008 champion Jo-Wilfried Tsonga.
American Jack Sock matched last month's run to the last eight in Shanghai as he dumped out home hope Richard Gasquet 6-2, 3-6, 7-5.
He will meet compatriot John Isner in the next round after the latter halted the run of German qualifier Jan-Lennard Struff, winning 6-4, 6-7 (4/7), 6-3.
Tomas Berdych, the 2005 titlist, plays Gilles Simon in the evening session with the Czech hoping to make the Tour finals for a seventh consecutive year.
The world number 11 trails Dominic Thiem, who lost in the second round, in the race for the remaining London berth and needs to reach at least the semis to leapfrog the Austrian.