The Dutch side go into the game a point behind Milan knowing that only a win would put them into the second round, and De Boer said that because of that there is no pressure on his players.
"With a Europa League ticket already in our pockets, we have nothing to lose now," he told De Telegraaf. "When you looked at the group after the draw, the pressure was especially on Barcelona and Milan.
"For us, finishing third at the expense of Celtic was feasible, with Barcelona and Milan deciding who would come first and second.
"Only very few teams can win at San Siro. Barcelona drew and always had it tough. That says enough I think."
The game kicks off at 7.45pm on Wednesday night.