Novak Djokovic needs to reach the Paris Masters final to stay ahead of Andy Murray at the top of the rankings.
Novak Djokovic recovered from a slow start as he continued the bid to retain his world number one ranking with a 4-6, 6-2, 6-3 win over 14th-seeded Bulgarian Grigor Dimitrov in the Paris Masters third round on Thursday.
The Serb, needing to reach the final to stay ahead of Andy Murray at the top of the rankings, set up a quarter-final clash with Croat Marin Cilic who clinched one of the two remaining spots for the ATP World Tour Finals with a 6-3, 7-6 (9) win over Belgian David Goffin.
"(Cilic) is in great form. He has a big serve that he relies on a lot. He's a big guy but he uses the court very well," Djokovic told a news conference.
"He's quite aggressive. Every short ball he's stepping in. He plays quite flat. He loves, I guess, these kind of very quick conditions."
Murray advanced in much easier fashion by demolishing France's Lucas Pouille 6-3, 6-0. The Scot next plays Czech seventh seed Tomas Berdych who ousted Frenchman Gilles Simon 6-4, 6-3.
"I thought I returned well today. I had chances in almost all of his service games throughout the match," said Murray.
"On this surface, when it's a bit quicker, that's good. If you can get a lot of returns back in play, it puts pressure on the server."
Holder Djokovic, seeking a fifth title in Paris, produced an under-par display. He had treatment on a knee problem in the second set but eventually subdued Dimitrov who grew frustrated as the match went on.
"No problem, thankfully. Just an awkward footing in that point but all is well," said Djokovic.
Canadian fourth seed Milos Raonic beat Uruguay's Pablo Cuevas 4-6, 6-1, 6-2 and next faces local favourite Jo-Wilfried Tsonga.
The Frenchman overcame a woeful start to down Japanese fifth seed Kei Nishikori 0-6, 6-3, 7-6 (3).
Unseeded American Jack Sock followed up his second-round win against Austrian sixth seed Dominic Thiem with a 6-2, 3-6, 7-5 victory against number 12 Richard Gasquet of France.
After an early trade of breaks, Djokovic dropped serve again as Dimitrov moved 3-2 up with a backhand volley.
A backhand winner down the line gave the Bulgarian the opening set but Djokovic reacted swiftly, opening a 3-0 lead in the second and levelling the match when his opponent served his sixth double fault.
Brimming with confidence, the world number one went 3-0 ahead in the decider and did not look back.
Earlier, ninth seed Cilic struggled to close out Goffin as he watched five match points go begging before finally claiming a pulsating second-set tiebreak.
Eighth seed Goffin had won all three of their previous meetings and was among the players in with a chance to seize one of the last two spots in the eight-man field at the Tour Finals in London.
But it was the 2014 US Open champion who refused to buckle under pressure.
Djokovic, Murray, Stan Wawrinka, Raonic, Nishikori and Gael Monfils had already qualified for the November 13-20 tournament in London.