Metz - Defending champion Jo-Wilfried Tsonga has made a winning return to tennis on Wednesday, beating fellow Frenchman Edouard Roger-Vasselin 6-3, 6-4 to reach the quarter-finals of the Moselle Open.
Sam Querrey of the United States and Tobias Kamke of Germany also advanced to the last eight.
Tsonga was playing his first match since a troublesome left knee injury forced him to retire in the second round at Wimbledon and then pull out of the US Open.
"I'm very happy that my knee held up," Tsonga said.
"I had a very good match.
"I didn't expect to play so well today."
The top-seeded Frenchman, who split with Australian coach Roger Rasheed last month, broke serve once in each set.
"Step by step, I'm raising my game," he added.
"I still choose the moments when I accelerate.
"In the next matches, I'll have to accelerate more and more often."
Tsonga will now meet Kamke, who rallied from a set and a break down to see off Hungarian qualifier Marton Fucsovics 1-6, 6-3, 6-2.
Kamke broke back at 3-2 in the second set and capitalized on four double faults from Fucsovics in the final set to win the last five games.
The sixth-seeded Querrey led 6-2 when his opponent, French wild card Paul-Henri Mathieu, retired because of a right thigh injury.
The American broke Mathieu twice and served an ace to take the first set.
Querrey will play another Frenchman in the next round, either second-seeded Gilles Simon or Kenny De Schepper.
Carlos Berlocq of Argentina, Benjamin Becker of Germany and Frenchmen Nicolas Mahut and Albano Olivetti advanced to the second round with straight-set wins.
Berlocq, who won the Swedish Open in July, did not face any break points in his 6-3, 6-4 victory over Jiri Vesely of the Czech Republic, while Becker upset fifth-seeded Benoit Paire of France 6-3, 7-5.
Mahut beat Leonardo Mayer of Argentina 7-6 (2), 6-4 and wild card Olivetti defeated 2010 runner-up Mischa Zverev of Germany 7-5, 7-6 (3).
Mahut won two titles in the summer and is enjoying his best season.
He blew a 4-2 lead in the first set but still won the tiebreaker before breaking Mayer in the opening game of the second set.
Ranked 254th in the world, Olivetti saved four break points in the first set and fired a total of 20 aces.
Results from the third day of the ATP Metz Open on Wednesday (x denotes seeding):
Jo-Wilfried Tsonga (FRA x1) bt Edouard Roger-Vasselin (FRA) 6-3, 6-4
Tobias Kamke (GER) bt Marton Fucsovics (HUN) 1-6, 6-3, 6-2
Sam Querrey (USA x6) bt Paul-Henri Mathieu (FRA) 6-2 - retired
Carlos Berlocq (ARG) bt Jir Vesely (CZE) 6-3, 6-4
Benjamin Becker (GER) bt Benot Paire (FRA x5) 6-3, 7-5
Albano Olivetti (FRA) bt Mischa Zverev (GER) 7-5, 7-6 (7/3)
Nicolas Mahut (FRA) bt Leonardo Mayer (ARG) 7-6 (7/2), 6-4