The American Under-20 international is yet to make his debut for the Portuguese club since completing a transfer from Major League Soccer's Real Salt Lake in August, but Adu says he is willing to wait for his chance.

"I don't know yet when I will play," the 18-year-old said. "I am young, I have just arrived and I needed some time to get used to my colleagues."

Benfica have played three league games this season without including Adu, who says he has needed time to make adjustments because of the differences between MLS and the European game.

"[In Europe] players are bigger than I was used to and the speed of the game is incredible," he said. "I needed a few weeks to adapt, but I am already used to it. I think and play more quickly."