The Taegeuk Warriors quickly found themselves 3-0 down in the Group H clash in Porto Alegre, and the defeat means that even a victory over Belgium in their final group game may not be enough to see them progress.
And Hong was hugely disappointed that his side made a series of mistakes to hand Algeria such a sizeable half-time lead.
“The result speaks for itself, we made mistakes today. We tried to change it up at half-time, but since we had conceded so many, it was difficult to turn it around,” Hong told reporters after the match.
“Our defence crumbled in the first half, we weren’t well organised. I tried to change that in the second half, but it didn’t work out.”
The result represented a first World Cup finals win for the Fennecs in 32 years, but Hong insists his side had not underestimated their opponents.
“No, we did not underestimate them, we knew they were strong all along,” he added.
“I think they were very well organised in defence, and our players weren’t up to the standard. Now the match is over, we have to prepare better the next time, that’s what is left for us to do.
“We still have a game to play, so I want my players to make a quick recovery and be better in the last match.”
That final fixture is against Belgium, but South Korea must hope that Algeria do not beat Russia, and that goal difference takes a swing in their favour, if they are to progress with a victory.
“We have to recover very quickly, and we have to make sure that our players calm down, and prepare for the next match.
“In the stadium today we saw a lot of Korean fans, and I would like to apologise to them. And for the next match, I promise we will do our best to achieve a better result.”