"We had a very high efficiency and I thought we defended very well."
New Zealand co-captain Sam Charlton admitted the Blacks Sticks discipline let them down, three green cards proving costly as they reduced them to 10 players each time.
"That's not how we planned it to go. We lacked a bit of discipline but I don't think the effort can be faulted," Charlton said.
The United States and South Korea drew the opening match of the tournament 1-1, with Erin Matson putting the US ahead. However Cha Yesol equalized two minutes from the end to give the Koreans an encouraging start.
A full round of four games will be played at the North Harbour Hockey Stadium tomorrow. In Pool B, Rio Olympic champions England will play bronze medallists Germany and Argentina face China, before New Zealand play Korea and the US face the Dutch.
Charlton said New Zealand would be confident going into the game against ninth-ranked Korea, given their good record against them.
"We know they are a team we can beat but we're looking for an improved performance."