The Brazilian winger has struggled for consistency, registering just one goal and three assists in nine appearances.
His difficulties continued with a controversial red card against Villarreal, raising further concerns about his performances.
However, speaking to TNT Sports, Mourinho dismissed worries surrounding the 25-year-old, insisting the forward possesses the quality to overcome his struggles and rediscover his attacking brilliance.
"He is going to emerge. It's just a question of when," the Portuguese said.
"After the previous match, I decided to take a different approach—to protect him a little and then bring him on when the game called for a player like Vini.
"I think that worked out well: the stadium, which had sometimes voiced disapproval, immediately rallied behind him the moment he started warming up.
"I believe that was a crucial turning point for him. It seemed like something clicked for him, reigniting that joy and reminding him of the kind of player he truly is."