Santos played for Rosenior while on-loan with Strasbourg last season.
"He has given a big confidence boost, not only for me but for a lot of other players as well," said the 21-year-old.
"I try to help my team-mates because I know the type of football he wants. It’s easy for me because I know him and I worked with him. He wants every player to work hard, to fight, and we have to give him some time to win games and to win trophies as well.
"But the goal this season is to win every trophy that’s possible. When you talk about Chelsea, you have to win trophies."
Santos admits he also feels happier at Chelsea after the arrivals this summer of fellow Brazilians Esteavo Willian and Joao Pedro.
He said: "I told Estevao he is a superstar! It’s not easy when you come from another country, another language, it’s hard but he is doing very well. I am so happy to play with him here and in the national team.
"And Joao is my brother. He is a top player and a top guy as well. I’m so happy for Joao Pedro, he’s so important and hopefully he can keep getting confidence from the goals he is scoring."