South Korea coach Hong Myung-bo blasted his team's woeful defending in their 4-2 World Cup group H loss to Algeria, saying the players had let him down.
"The defence wasn't what it should have been, our players were not up to standard," Hong said after the defeat, which left South Korea bottom of the group.
"I would like to apologise to the Korean fans and I promise we will do our best for the next match," he said.
South Korea's defending had been a major cause for concern in the lead-up to the World Cup and slack play cost them a goal against Russia in their 1-1 draw.
"We did analyse the strategies, but the result was such that I could say it was not well done," Hong said.
"The result speaks for itself, so that was incorrect on our part. But we have to look ahead. As we conceded a lot of goals, there was a strategic mistake on our part."
Hong rejected any suggestion that South Korea had taken Algeria too lightly.
"No we did not underestimate the team, we knew they were strong," he said. "We were on the defensive and the defence was weak. They were not concentrating and did not defend well."
Hong said there was a communication breakdown that allowed Algeria to take a 3-0 first-half lead. "There was not enough communication between the defensive players," he said. "It was something we can learn from, but the three goals in the first half were really regrettable."
Hong said his team still had hopes of advancing.
"We still have one game left [against Belgium] and I want my players to recover well," he said. "We have to recover very quickly in the time remaining, make sure our players calm down and prepare well.
"We haven't thought about a change in line-up, but we will do our best to the end."
Algeria coach Vahid Halilhodzic remarked: "I dedicate this victory to all the Algerian supporters who have waited for this for 32 years. This was a victory for pride.
"Now we play a third match, a play-off against Russia and anything is possible."