Belgium's coach Marc Wilmots (C) celebrates his with staff after they beat Russia in their 2014 World Cup Group H soccer match at the Maracana stadium in Rio de Janeiro June 22, 2014.
"To advance in a tournament, you don't always need to be pretty. I believe that you need to be efficient." he told a news conference.
"What counts is that Belgium got a good win and qualified for the second round. Everything else has absolutely no importance."
Brazilian fans jeered the teams during a second half of their Group H match that was littered with mistakes.
But that was before the closing stages when winger Eden Hazard switched on the kind of form that has lit up Chelsea matches this season as he created several late chances.
It was his cross that set up the 88th-minute winner by substitute Divock Origi, the 19 year-old son of a former professional footballer who was the youngest player to score in this tournament and the first teenager to net in the World Cup finals since Lionel Messi in 2006.
Wilmots said Belgium were the second youngest team in the World Cup, giving them an edge in the heat of Brazil as games go into their closing stages.
Belgium also scored two goals in the last 20 minutes to beat Algeria in their first game.
"Why did it change? Because we were physically stronger," Wilmots said. "There's something clear in football. Levels of physical fitness count in a World Cup."
Hazard said his fitness helped him settle games.
"I know how to make the difference. When I make the difference, I often do it at the end of the match and that shows that I am fresh," he told reporters.
Wilmots said Belgium would be looking for three more points in their final group match against South Korea but he might rest players who have picked up yellow cards and who would miss the first knock-out match if they were booked again.
Axel Witsel and Toby Alderweireld were cautioned on Sunday while Jan Vertonghen was shown a yellow card against Algeria.
If Belgium finish top of the group, they will face the second-placed team in Group G which comprises Germany, the United States, Ghana and Portugal.