The Red Devils claimed a 1-0 victory over South Korea on Thursday to top Group F and set up a last-16 meeting with the USA.
They were forced to play the entire second half with 10 men following Steven Defour's sending-off, but they managed to ensure a third successive win in this year's tournament through Jan Vertonghen's late goal.
"The sending-off really spoiled our strategy for the game, but I was able to rearrange the team at half-time," Wilmots told FIFA.com.
"If we get space, we are dangerous and I knew that Korea Republic would push forward in the second half. They had to. We were patient and we exploited that.
"I wanted to keep the players fresh for the knockout stages so I made changes, but now everyone is prepared and ready for the round of 16. We're on track."
Belgium and the USA meet in their last-16 clash next Tuesday in Salvador.