South Korea beat Costa Rica 1-0 in Los Angeles on Saturday to win the first of three friendlies on their tour of North America as they continue their preparations for the World Cup in Brazil.
Towering striker Kim Shin-wook scored the only goal in the 10th minute of an ill-tempered match in which two Costa Ricans were sent off.
Defender Christopher Meneses was shown a straight red card after 68 minutes and replacement midfielder Mauricio Castillo was ordered off after picking up a second yellow card four minutes from the end.
It was an encouraging result for South Korea, who were drawn with Belgium, Russia and Algeria in Group H for the World Cup, after they selected a weakened squad for the tour.
They will play Mexico in Texas on Wednesday before finishing off their short trip with a match against the United States in California next Saturday. However, it was another disappointing result for Costa Rica, who are also World Cup-bound and will play in Group D with England, Uruguay and Italy.
They were without their best players from Europe on Saturday but have now suffered three straight defeats since booking their place to Brazil. Adding to their woes, defender Bryan Oviedo, who plays club football in England with Everton, could miss out on the World Cup after breaking his leg on Saturday.
The player has been capped 26 times by his country and was almost certain to be named in the squad.