Denmark manager Age Hareide has heaped praise on last-16 opponents Croatia, labelling them the "best" side in the tournament so far.
The Croatians are one of two sides, alongside Uruguay, to have taken maximum points from their group following three impressive performances against Nigeria, Argentina and Iceland.
Hareide told the Daily Mail that his side must step up their performance if they are to reach the last eight.
"The Croatians have a fantastic midfield and have probably been the best team in the tournament," the manager said.
"We know they have very skilful players and are very flexible but you will see a different Denmark. We need to attack more and we will."
Denmark are on an unbeaten run stretching back 18 games ahead of Sunday's clash.
