"It was a bit of a lesson," he said.
"We probably should have scored a couple of goals but they really gave us a few areas to work on. They identified a lot of weaknesses we had, but we had seven players who'd never played them before so it was a bit of a wakeup call."
As Hager put it, "They're the best in the world and there's a reason why they are. They had four of their best players out but they've got talent to burn".
He has a decent idea of the challenge China will pose.
"They're quick, skilful, their basic skills are very good and they don't mistrap too often. We don't play them enough to know what to expect but they've got a good drag flicker as well so we don't want to concede too many penalty corners."
New Zealand's other pool games are against hosts Argentina, the world No 2, and sixth-ranked Australia.
The team is without experienced players Stacey Michelsen, Katie Glynn and Emily Naylor but it will be a good test of the depth within the squad.
