Manchester United, Juventus and Chelsea are among the clubs reportedly interested in James, who has struggled for game time at Madrid this season.
Mendes, who has said James will not be leaving the LaLiga leaders in January, said the Colombia international needed to work his way back into Zinedine Zidane’s plans.
“He’s a top player. He can play anywhere. He doesn’t have to prove anything,” he told Sky Italia.
“He’s a player who has done well. Now, he has to recover to convince Zidane.”
James has made just eight LaLiga appearances for Madrid this season, scoring one goal.
Asked about the links to Juve, Mendes said: “I don’t speak of clubs. We’ll see what will happen.”