Juve have drawn Spurs in the round of 16.
Ghana international Asamoah stated: "Tottenham are solid, they defend well, they have beaten important teams in their group.
"But if you want to try to win the Cup you have to be able to beat everyone. All the challenges are difficult.
"We are improving our defending. We've conceded some goals, but now we're doing better. You can see our form is improving."