Eintracht Frankfurt coach Niko Kovac has welcomed new signing Guillermo Varela.
The Uruguay fullback has joined on a season-long loan from Manchester United and has already started training with his new teammates.
Kovac said: "The aggressiveness of Varela is enormously important. But he also needs to know where the boundaries are here.
"There are some stadiums where there are so many cameras you can even get a card when you take a look at someone obliquely.
"It can get petty in the Bundesliga, so we must talk with him."
Varela admits he enjoys the physical side of the game.
"It's true. We players from Uruguay are never squeamish about our opponents. At Man United I also fouled Wayne Rooney in training. Like everyone else!"
He added: "I was not satisfied with my year at United. I need to play more."