Germany and Portugal also await in the fiendishly difficult-looking Group B and World Cup runners-up Netherlands want a fast start against the modest Danes in Kharkiv on Saturday to get points on the board before the trickier encounters ahead.
Van Marwijk is aware however that 1992 winners Denmark are dangerous on their day and Morten Olsen's men have all the information they could ever need on their orange-clad foes.
"We have no secrets. A lot of their players play in Holland and also in other European leagues, their style of play is a little bit the same, both teams respect each other," Van Marwijk told reporters.
"For me it is the most important game."
The two sides met in the 2010 World Cup group stage with the Dutch winning 2-0.
Centre-back Joris Mathijsen is almost certainly out of the Kharkiv match because of a hamstring problem so Ron Vlaar or Wilfred Bouma are likely to step in.
Otherwise Netherlands will unleash their armoury of potent weapons including Arjen Robben and Robin van Persie, whose silky skills have been wowing the vast crowds at their training sessions in Krakow and helped destroy Northern Ireland 6-0 in their last friendly.
The Danes believe they offer enough of a threat themselves to stun the Dutch, especially with their defence looking shaky given Mathijsen's injury and left back Jetro Willems in line to pick up only his second cap.
"There are a lot of players who can take charge in midfield, and provide both goals and assists," said Denmark striker Nicklas Bendtner, who has six goals in his last eight internationals.
"It's looking good, we've been practising well and intensely. We just need the last technical and tactical details and we'll be on our way."
Christian Eriksen, of Dutch champions Ajax, will pull the strings for the Scandinavians in midfield as he looks to fulfil his promise and become one of Europe's most talked about players.
"I've known I'd be under pressure from the beginning. The more you play, the more focus and pressure there'll be on you - I hope it stays that way," the 20-year-old said.
"Of course, it's been a different kind of spotlight than that which I have been under before, but it's fine."
