Novak Djokovic began his bid for a record-extending seventh Paris Masters title with a fluent display in his first singles match in over six weeks.
Serbia’s Djokovic, who had not played since a Davis Cup match on 15 September, won 6-3 6-2 against Argentina’s Tomas Martin Etcheverry.
The 24-time major champion will face Tallon Griekspoor in the last 16.
Third seed Daniil Medvedev appeared to raise his middle finger to the crowd after he lost to Grigor Dimitrov.
Medvedev, 27, reacted to being booed by the French fans having eventually buckled against the Bulgarian, who took his seventh match point to clinch a 6-3 6-7 (4-7) 7-6 (7-2) win.
The jeers towards Medvedev started when he flung his racquet in the second set and he refused to continue until the boos stopped, leading to a time violation from umpire Renaud Lichtenstein and a subsequent argument.
Asked about the gesture as he walked off court, the former world number one said: “I just checked my nails, it’s nothing more than that. Why would I do that to this beautiful crowd in Paris?”
The Russian’s defeat means the two leading seeds behind Djokovic are already out, with Spanish second seed Carlos Alcaraz suffering a shock exit against 45th-ranked Roman Safiullin on Tuesday.
Djokovic, 36, further boosted his chances of finishing above Alcaraz as the year-end number one with his winning return to the tour.
Having not played a tour-level singles match since lifting the US Open title on 10 September, Djokovic looked sharp throughout against world number 31 Etcheverry.
Djokovic, showing his usual precise hitting and athleticism, won three of seven break points and saved the only one he faced.
Sinner wins late as Rune, Zverev & Tsitsipas progress
Italian fourth seed Italian Jannik Sinner battled back to beat American Mackenzie McDonald in a match which finished at 02:37 local time.
Sinner, who triumphed at last week’s Vienna Open, lost a first-set tie-break but progressed 6-7 (6-8) 7-5 6-1 after edging the second and closing out victory by winning five successive games.
The 22-year-old is due back on court on Thursday against Australian Alex de Minaur in the fourth match of the day session.
“I lost the first set in a bad way and I’m still getting used to the conditions, but I’m happy about the win and to be in the next round,” Sinner said.
“It was tough going on court after midnight, but it was nice to still have some crowd watching.”
Danish sixth seed Holger Rune, who beat Djokovic in last year’s final, started his title defence with a 6-4 6-2 win over Austria’s Dominic Thiem.
Rune also moved a step closer to securing his place at the season-ending ATP Finals in Turin, as did Greek seventh seed Stefanos Tsitsipas with an impressive win over Canada’s Felix Auger-Aliassime.
Serving well under pressure to save six of seven break points, 25-year-old Tsitsipas earned a 6-3 7-6 (7-4) success to reach the last 16.
Tsitsipas will next play German 10th seed Alexander Zverev, who it was reported on Tuesday has been charged with assaulting an ex-girlfriend.
Zverev, who is aiming to book his spot in Turin, saved 11 break points before France’s Ugo Humbert took his next two chances to level the match and move a break up in the decider.
But 26-year-old Zverev fought back to seal a 6-4 6-7 (3-7) 7-6 (7-5) win after three hours and 28 minutes.
Poland’s Hubert Hurkacz became the first man since 2019 to hit 1,000 aces in a single season as he beat Spain’s Roberto Bautista Agut 6-3 6-2.
Australia’s De Minaur progressed by beating Serbia’s Dusan Lajovic 4-6 6-4 6-4 in what was the 200th win of his career.
Murray misses out on Turin & Skupski splits with Koolhof
British doubles player Jamie Murray saw his hopes of reaching the ATP Finals ended by a second-round defeat in Paris.
Murray, 37, and New Zealand’s Michael Venus, who are ninth in the race with the top eight qualifying for Turin, lost 6-4 6-3 to Mexico’s Santiago Gonzalez and France’s Edouard Roger-Vasselin.
Meanwhile, Britain’s world number three Neal Skupski is looking for a new partner for the 2024 season after Dutchman Wesley Koolhof ended their successful partnership.
The pair won the Wimbledon title earlier this year and could still finish the season as the world’s best pair, but Koolhof has decided to team up again with his former partner Nikola Mektic of Croatia.
