Midfielder Koo was last month named captain by coach Hong Myung-Bo ahead of the showpiece in Brazil and played his part in securing a 1-1 draw with Russia in their Group H opener.
Victory against Algeria at Estadio Beira-Rio in Porto Alegre on Sunday will put South Korea on the verge of the last 16 ahead of their final group clash with Belgium.
And Koo is bullish over his side's chances of seeing off an Algeria side that surrendered a one-goal lead to lose 2-1 to Marc Wilmots' pool leaders.
He told FIFA.com: "Things like morale and the preparation, that are not in the hands of the coaching staff, are my responsibilities.
"If I observe the players and I control them, so to speak, to make sure that they enter the match together, then I think we will get a good result against Algeria.
"I don't feel especially pressured or overwhelmed by the responsibilities."
