Eden Hazard admitted Belgium did not play well in their 1-0 over Russia but insisted that the result was all-important to secure qualification for the knock-out rounds of the World Cup.
The Chelsea midfielder created the only goal for 19-year-old striker Divock Origi two minutes from time to settle a tight contest against Fabio Capello's side.
Hazard, who came alive during the final 10 minutes and threatened several times before the goal, said: "It was a difficult match but we are very happy with the result and the victory today means we have already qualified and still have one match to go in the group.
"We will now aim for three wins in this group campaign.
"We didn't play a very good match but the last 10 minutes were better and maybe the Russian defence got tired and we got more space for the substitutes, who were fresh, to exploit.
"I felt fit though - I'm in good shape and as I often make the difference towards the end of the match it shows I am still fresh."
Belgium boss Marc Wilmots said it was "a highly tactical game" and that he might rest players for the third game against South Korea if they were tired or on yellow cards.
He said: "We were fresher, we were better and that made the difference - maybe due to our very good fitness preparations.
"We want to be number one in the group but if there are yellow cards or for reasons of freshness I may make a decision."
Origi had come on for Romelu Lukaku after 55 minutes and the Chelsea striker trooped off the field looking hugely disappointed.
Wilmots added: "If he has to go off after 55 minutes he's not happy of course - that's natural. It's not a problem, it's normal and it happened to me as well.
"I understand his reaction completely and I will analyse things with him, but I need all my players and the truth of today is not always the truth of tomorrow."
Capello's Russia side need to beat Algeria and hope Belgium defeat South Korea to have any chance of progressing, and the Italian insisted his players had done well.
He said: "Frankly I am very happy with the performance the team and I thought the result was unfair.
"The truth of the matter is we had chances to win it but we lost. Both teams gave it their all and unfortunately it was Belgium that was able to make it.
"We have to look forward and I said when we came to play in this World Cup after being absent for 12 years that this will be a great help for us to understand the level we need to be at in future competitions.