The 45-year-old claims he had a feeling goalscorer Lee Keun-ho could make an impact against a tiring back line and says he had planned the substitution in advance
Keun-ho emerged from the bench early in the second half and broke the deadlock after 68 minutes, albeit thanks to a terrible mistake by Russia goalkeeper Igor Akinfeev.
And Myung-bo says he knew exactly what he was doing when he threw the 29-year-old on in place of Park Chu-Young.
"I planned Lee Keun-ho's substitution because Russia's centre-backs are slow and I knew they would be tired in the second half," the coach told SBS after the game. "He did his job well and scored a goal."
Myung-bo added that he was pleased with his players' performance following a lively display and claimed he was never concerned despite losing 4-0 to Ghana in a pre-tournament friendly in Miami last week.
"I want to thank the players - they did their best until the very last minute," he said. "The heavy defeat against Ghana was not important, it was just part of the process. We focused our rhythm and organisation on this match. I think it worked well. The condition of the players and the organisation was good.
"Now recovery is the most important thing as we focus on the Algeria match."
Keun-ho, meanwhile, said scoring at a World Cup was a dream come true.
"I have always dreamed and longed for this moment, ever since I was omitted right before the 2010 World Cup," he said.
"I had a good feeling for shooting during pre-match training, so I was confident. Maybe the good luck followed because of that confidence."