But European champions Portugal are unlikely to be a much easier opponent when they clash in Switzerland, particularly given the form Ronaldo is in.
Ronaldo scored twice late on as Portugal came from behind to beat Egypt last time out, while he has 17 goals in his previous eight at club level.
And Koeman accepts that there is often little that can be done to stop a player like Ronaldo.
"It's the 'hand of the master'," Koeman told reporters on Sunday.
"He is one of those players that always scores. Even when the team is playing badly, they have the ability to score out of nothing.
"And sometimes they don't need other players to achieve that. There are one or two players like that at the moment."
Koeman was only installed in his new position in early February, with the former Everton boss charged with sparking an improvement following the country's failure to qualify for the World Cup.
And he accepts Netherlands cannot be seen as being among the best anymore, highlighting a need to "find other ways" to succeed.
"We are not the best of the world anymore. That's nothing new," he said. "So we have to find other ways to achieve something.
"We play in a new formation, in which we want to develop ourselves and hopefully Monday will be better than last Friday. Especially our football skills."