Ferguson believes the 23-year-old will only begin to show his true colours after having a full season to settle at Old Trafford.
"He's come from an environment that is completely different," he stated. "I think the difference between German football and English football has been shown. In Germany you can't foul. It's foul after foul.
"The Premier League is completely different as there's physical contact in our game and it's different to Germany but, next year, he'll be better."