Aleksandar Kolarov’s sublime free-kick made the difference for Serbia in Samara on Sunday.
The win was Serbia’s first opening match victory in a World Cup since France in 1998.
The match was also Krstajic’s first competitive game in charge of the national team, having taken over in October when qualification was secured.
“There was a great deal of pressure on the players and I felt pressure over the past five or six months,” Krstajic said during his post-match interview.
“It was my debut with the national team. I am a person who likes to take responsibility.”
He also defended Aleksandra Mitrovic who missed three clear-cut chances to score.
“I know his (Mitrovic) qualities, everyone does. He lacked luck but we will keep him for the remaining games as he is an important cog in our machine,” Krstajic said.
On his side’s next game against Switzerland, Krstajic said: “Regarding Switzerland, we have analysed all three opponents and how they have played over the past few months.
“We know everything about Switzerland and now we will watch then against Brazil to make sure we don’t miss everything.”