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.