South Korea coach Hong Myung-Bo held his hands up after Sunday's unexpectedly cut and dry 4-2 loss to Algeria, blaming an error in strategy on the defeat that leaves their World Cup knock-out rounds hopes looking slim.

Hong is an iconic figure back in Seoul after captaining the side that made it into the last four when the World Cup was co-hosted by the Koreans 12 years ago.

He will now have to call on all his footballing acumen to mastermind a Korean upset of already qualified Belgium on Thursday to still be in a shot of going through to the last 16 depending on the outcome of the other Group H game between the Algerians and Russia.

"We studied their style of playing but the result suggests it wasn't ideal," Hong said.

"The result is sufficiently eloquent, our strategy wasn't the right one.

"As we let in a lot of goals there was an error in our approach."

He also took aim, as Algeria did so effectively in the first half when they were up 3-0, at his defenders.

"I would have preferred the defenders to have been more stable. The results show that they haven't concentrated enough."

He denied that he and his team had under-estimated an Algerian side that hadn't won at a World Cup since 1982.

"We knew that they would be strong, we were on the defensive as our defence was weak."

"Algeria were well organised, structured, and our defenders weren't at their best.

"But now we have to turn the page, this result is the reward for our preparation. We must prepare better for the next game, it's our only option."

This is the Koreans' eighth successive World Cup but they have only managed to make the second round twice in that run, in 2002 and in 2010 when they lost to Uruguay in the last 16.