Gael Monfils won the all-French clash with Adrian Mannarino at the Paris Masters on Wednesday night.
In the prelude to the tussle on centre court at the AccorHotels Arena in Bercy, Monfils said he expected a tough battle against his compatriot even though he had won three of their five meetings.
The 15th seed was prescient. Mannarino started the encounter with zest and Monfils' cause was not aided by a fall early in the match.
Mannarino claimed the opening set 6-2. But Monfils, like in his match against Miomir Kecmanovic, maintained his composure and took the second set in the tiebreaker.
Perhaps sensing he had lost his opportunity, Mannarino started to make more errors as Monfils surged into a 3-0 lead in the decider.
The 35-year-old eventually claimed it 6-2.
His reward will be a last 16 showdown with the top seed Novak Djokovic who returned to action on Tuesday night against Marton Fucsovics from Hungary.
Djokovic, who has not played since losing the US Open final in September to Daniil Medvedev, won in three sets.
On Thursday he will attempt to inflict an 18th defeat on Monfils in 18 meetings.
Earlier French qualifier Hugo Gaston came from a set down to upset the 12th seed Pablo Carreno Busta 6-7. 6-4, 7-5.
The 21-year-old , who will break into the top 100 for the first time in his career after the tournament, will play the fast rising Spanish teenager Carlos Alcarez for a place in the quarter-final.
Alcarez, 18, dispatched the eighth seed Jannik Sinner 7-6, 7-5.
Elsewhere, third seed Stefanos Tsitsipas withdrew from his match against Alexei Popyrin with an injury to his right elbow while trailing 2-4 in the first set.
Popyrin, who played his first round match against Alex de Minaur as a lucky loser following defeat in the final round of qualifying, will take on his fellow Australian James Duckworth in the last 16.
Dominik Koepfer, another lucky loser, also advanced to the last 16. The 27-year-old German saved seven match points as he edged past former champion Andy Murray in the first round on Monday.
He had less trouble against the ninth seed Felix Auger-Aliassime.
He dispatched the 21-year-old Canadian 6-3, 7-5 and will take on the seventh seed Hubert Hurkacz, a straight sets winner over the American qualifier Tommy Paul.
