Christian Pulisic admits he has found it difficult to adapt at Chelsea.
Pulisic, signed from Borussia Dortmund in the summer, scored a hat-trick against Burnley on Saturday in what was his first Premier League start since August.
"The competition, the physicality, and the schedule is different to what I've known," he told the club's website.
"It's about getting used to this whole environment here, and I am enjoying every moment of it. As I get older I want to improve every single day.
"Being here and working with these guys and playing at the highest level, I have learned so much already."