De Boer fears the young Dane could be tempted by London's attractions.
"It's very tempting to go to lunch with friends in the city, while you really should prepare for the game at home," said De Boer. "London is a great city.
"You've got a lot of family and friends close to you, but for an athlete there is only one thing that matters: Performing."
For the big stories and the banter follow us on Twitter: @tribalfootball