After scoring twice in the Spanish Super Cup final triumph against Real Madrid in Jeddah, Raphinha paid tribute to Flick.
"If Hansi Flick hadn't come, I would have left Barca. He changed everything," he said.
"He told me that I was going to be important. That's what a player needs - confidence."
Under former coach Xavi, former Leeds United star Raphinha made 87 appearances, scoring 20 goals and providing 23 assists. With Flick, he has played 74 matches but has surpassed those totals, scoring 45 goals and registering 26 assists.
Speaking on Sunday, Flick said of Raphinha: "He has a dynamic, which affects the whole team. You can see he missed the first chance he had in the game, but for the second one, he was there, he shoots the first goal and gives the team more confidence.
"This is what he brings. Rapha on the pitch is a lot of intensity, and we need this."