Luis Enrique‘s side finished second in Group E and will now battle it out with the 2018 World Cup finalists at the last 16 stage.
Atletico Madrid skipper Koke has played a key role for Spain so far at the tournament with three starts in their three group games.
However, with the pressure increasing in the knockout stages, the 29-year-old knows he and the rest of the Spanish team need to be on top form to shut out Real Madrid icon Modric in the Danish capital.
“We have to try to take the ball from them and keep it for as long as possible”, he told a pre match press conference with Marca.
“Modric is one of the best players in the world and his outside of the foot passing and shooting is incredible.
“I personally like to play against the best and Luka is one of them.
“Sometimes he has won, others I have, and hopefully this time Koke wins.”
POSSIBLE SPAIN STARTING XI V CROATIA
Simon; Llorente, Garcia, Laporte, Alba; Busquets, Koke, Pedri; Torres, Morata, Moreno