1) Lots of great teams are having that same problem during this World Cup. There isn't a team with a really solid defense, and a very dangerous attack. Argentina's defense sucks, with Demichelis giving out easy goals, fricking weak defense from Gutierrez. Brazil took two stupid goals in both games, Spain dominating in offense and taking a counter goal from Switzerland. Korea defense was solid against Greece, and the reason they took so many goals from Argentina was because they went for the win. Maybe they started slow so far, but that doesn't mean they'll always do it.
1. They've consistently started slowly, even in the qualifiers which I watched. They always play nervously, even against a weaker team, and I see no reason as to why South Korea would stop now, with a very strong opponent. Just watch the first 15 minutes of each game, you'll see quality strikes by opponents, due to the Korean defense. For example, Nigeria's first goal. Korea should have been able to defend that, but their defensemen were too far back in the field to effectively counter the fast running Nigerian offense. I'm not saying there won't be an upset. If South Korea can straighten out their problems, they are a very very potent team, and as a Korean, I hope with all my heart that they'll win. However, my realistic side of me tells me that South Korea, in their state, will not be able to advance further.
2) You know, there are TWO Parks on their team, right? The Manchester United one is a star player. And Chu Young Park also proved to be able to kick from outside of the box. He scored once from a Free Kick, and had plenty of chances to score against Greece too, and against Nigeria, some of them were saved by the keepers. Ji Sung Park scored twice already, they have lots of chances with Free Kicks and corners, with a defender having scored twice already. And they also scored more than Nigeria so far. They aren't on the next round by luck alone, and they deserved a lot more, IMHO.
The part that ticks me off is that they have so many quality free kick chances. During the Nigeria game, they've had 4 quality free kick chances. Two they kicked away, one they lobbed for a play, and one was a very good strike (I have to admit) but with a stroke of luck, because the Nigerian goalie accidentally went one way, which he shouldn't have. During Argentina, when they had direct free kicks, they hit the wall 2 times, and shot the ball over the net more times. I wish that they'd stop shooting the goddamn ball, and do a more plays. Korea has seen success in corner kicks, and in free kicks, setting up for a header, or one timer, as seen in Greece and Nigeria. Even in Argentina, they had a very good corner kick chance. But it ticks me off that they keep kicking them away.
3) Ji Sung Park, Cha Du Ri, Chu Young Park, Lee Chung Yong, Yeom Ki Hun and Ki Sung Yong. The great majority of those players have already played in Europe, Cha Du Ri was able to outfoot Greek defenders, and they are a lot more experienced in defense than Uruguay, whose defenders are a lot slower than Nigeria's.
You cannot say that Greece was in their top form during that game. After that one goal, they played a very discouraged game, misplaying the ball, making bad passes, and generally being outplayed by the offense. Uruguay is on the momentum train as of the moment. And furthermore, again, those players may have played in Europe, but that doesn't automatically mean that they'll be penetrating the defense, as we've seen in the past 2 games. During the Nigeria game, they haven't EVER had a quality scoring chance in the box, during an offensive rush.