Novak Djokovic celebrated his elevation to world number one by reaching a new personal landmark to reach the Paris Masters quarter-finals on Thursday.
The Serb won his last 16 tie with Damir Dzumhur after the Bosnian was forced to retire trailing 6-1, 2-1 at Bercy.
For second seed Djokovic it meant he extended his sequence of consecutive winning sets to 30, passing his previous best mark of 29 from 2015.
The four-time Paris champion faces Marin Cilic in the last eight on Friday.
Djokovic takes over as world number one in the latest ATP rankings published Monday from Rafael Nadal, who withdrew injured from Paris on Wednesday.
Cilic, the fifth seed, secured his quarter-final ticket with a 7-6 (7/5), 6-4 defeat of Grigor Dimitrov.
Cilic fired 29 winners to advance to the last eight in the French capital for the third straight year.
The win improved the Croat's prospects of making the ATP Finals in London starting on November 11.
"I am very close to London, to securing my spot mathematically," said Cilic, who is part of the Croatia team facing France in the Davis Cup final at the end of this month.
"In the next match against Novak it will be another big challenge. (It will be) great to play him again."
Cilic, who will guarantee making the cut for London if he downs Djokovic, was ending reigning ATP Finals champion Dimitrov's season.
Dimitrov has been coached by a former coach of Djokovic, eight-time major winner Andre Agassi, in Paris this week.
Djokovic and Cilic were later joined in the quarter-finals by Karen Khachanov who saved two match points agaisnt John Isner on his way to defeating the eight-seeded American 6-4, 6-7 (9/11), 7-6 (10/8).
The Russian will next play Alexander Zverev after the German fourth seed beat Diego Schwartzman of Argentina 6-4, 6-2.
Earlier on Wednesday, Rafael Nadal pulled out of the Paris Masters guaranteeing Novak Djokovic's return to the world number one spot.
The Wimbledon and US Open champion becomes the first player to start the season outside the top 20 and end up top of the ATP rankings since Marat Safin in 2000.
For Nadal it means delaying his long awaited comeback from injury which has kept him sidelined since the US Open.
After Paris the ATP tour's eight top-ranked players congregate in London from November 11 for the season's Finals.
The 32-year-old Nadal has enjoyed a successful year, clinching his 17th Grand Slam title by winning an 11th French Open in June, after triumphs in Monte Carlo, Barcelona and Rome.
But it is Djokovic who will be top dog when the latest ATP rankings appear on Monday, irrespective of his fate in the French capital this week.
Despite the blow the tournament organisers will be relieved to see Roger Federer making his first appearance at the competition since 2015.
The Swiss great starts his quest for his 100th ATP title in the last 16 on Thursday after his Wednesday rival Milos Raonic withdrew through an elbow injury.
World number three Federer will face Italy's Fabio Fognini, ranked 14, who made the next round when Hungary's Marton Fucsovics withdrew injured.
Elsewhere, German fourth seed Alexander Zverev, playing his 70th match of the season, defeated Frances Tiafoe of the United States 6-4, 6-4 while defending champion Jack Sock put out Richard Gasquet 6-3, 6-3.
South African seventh seed Kevin Anderson, the champion in Vienna at the weekend, battled past Nikoloz Basilashvili of Georgia 6-3, 6-7 (3/7), 7-6 (7/3).
Anderson next faces Japan's 10th seed Kei Nishikori, who he defeated in the Austria final. Nishikori made the last-16 with a 7-5, 6-4 win over Adrian Mannarino of France.
Bulgarian ninth seed Grigor Dimitrov, who is working with US legend Andre Agassi in Paris, went through with a 7-6 (12/10), 6-4 victory over Spain's Roberto Bautista Agut.