Haaland has scored five goals in his past four games with City.
"There are more players to stop than him, but he's usually at the end finishing sequences," said Eckert. "You can only stop him as a collective.
"You have to be clear on how you want to defend if the ball is out on the wing and make sure you don't get dragged out because that opens up the centre.
"If we look at the last 20 games, we've not conceded much from open play. It's not that easy to score against us, but the bar rises again here.
"I have some very good friends who worked with him for many years in Salzburg and at then later at Dortmund.
"It's nice to see how he adds one layer after another to his game. He's still young for a striker, and it becomes harder to stop him.
"I've also worked in Italy for a couple of years, where they have different concepts of how to mark in the box.
"He didn't enjoy the games against Inter Milan too much. I'm sure that we are prepared in the way we need to take care of him in the box."