(Reuters) - Belgium came into the World Cup with a side short on experience but long on flair and were considered a good outside bet after an unbeaten qualifying campaign of eight wins and two draws.

They have cemented their position as dark horses with three wins out of three and at the same time shown they have strength in depth by giving all but one of their outfield players a run- out.

But Belgium, a country of 11 million people squashed between Germany, the Netherlands and France, have shown little of the flair that marked their qualifying campaign and the way they ground out three one-goal wins has been more Germanic efficiency than French flair.

"It's maybe not the sexiest football we've shown but we're very happy with nine out of nine points," Mousa Dembele told reporters after Thursday's 1-0 win over South Korea.

"Every game we win we're more and more confident."

The win over a poor South Korea side was a classic example.

Coach Marc Wilmots made seven changes from the side who beat Russia against team who needed three points to have any chance of progressing.

He transformed the defense in the absence of captain Vincent Kompany and Thomas Vermaelen, both of whom were injured, and gave a start to 19-year old winger Adnan Januzaj.

"This is a World Cup played in a very hot country, so you have to anticipate," Wilmots said. "I saved, I spared those I thought I had to spare. Now everybody is at the same level."

The changes almost backfired when one of the new boys, Steven Defour, was sent off for a foolish stamp shortly before halftime.

But Belgium recovered from the setback to show great resolve.

Their towering defensive line remained strong with full back Jan Vertonghen outstanding.

It was Vertonghen, allied with another substitute who won them the game. Teenager Divock Origi, making his third substitute appearance in three games, got free of the Korean midfield to fire in a shot that Jung Sung-ryong could only parry.

Vertonghen had charged forward and slotted the rebound home. It was a fitting reward for the Man of the Match.

Wilmots had said his fringe players were itching for a chance to "showcase what they can do" and they did not disappoint.

Their confidence is growing and they have an eminently winnable last-16 game against the United States coming up next.

Just do not bet on them turning on the style again.

"What does it mean to play beautifully?" Wilmots said.

"Every game is characterized by tactics and physical fitness. What is important in the end is the result, to win the match with whatever style of play. We are not here to look at them (other teams). We are here to win ... The rest is literature."