The Belgians hit back with substitutes Marouane Fellaini and Dries Mertens scoring in the second half in Belo Horizonte on Tuesday.
Wilmots, the coach, said he had to lift his team's morale at the interval. "The players seemed like beaten men in the dressing room," he said. "But I told them that I was sure that we would score eventually."
"The substitutions I made injected a bit of pace, which changed the game after the break," Wilmots added.
Belgium take on Russia at the Maracana on Sunday.