Lyon captain Maxime Gonalons is confident off-field issues will not disrupt France forward Mathieu Valbuena's form.
Valbuena, 31, was the victim of a recent blackmail attempt and four people, including his former France and Marseille teammate Djibril Cisse, were taken into custody in connection with the case this week.
After being released the same day, Cisse said he had tried to warn Valbuena to be careful.
On Thursday, one person was charged with attempting to extort money from the former Dynamo Moscow player.
Valbuena was also targeted by some Marseille supporters when he returned to the Stade Velodrome in Lyon colours last month.
But Gonalons told a news conference: "Mathieu is a guy who has huge mental strength.
"What he put up with at Marseille a few weeks ago was incredible for him.
"What he showed on the pitch demonstrates his strength of character. He was one of the best players on the field.
"When you see all that he took on his head during the whole game, you have to be mentally tough.
"I can tell you that everything that's going on at the moment is not affecting him.... don't you worry about him."
Lyon boss Hubert Fournier also said the winger was a person with the ability to shut out distractions.
"I found him very good at training," Fournier told reporters. "He's a small man in terms of his height, but he's someone who's very tough mentally."
Meanwhile, Lyon have hit out at French league authorities for the "surprising" decision to schedule their Ligue 1 game at home to Toulouse next week on a Friday night.
That means it will come only three days after a Champions League group match against Zenit St Petersburg in Russia.
A club statement said the scheduling was "clearly prejudicial" and that the decision showed a "total disregard for sporting fairness."
