New Zealand fly-half Dan Carter has revealed how difficult it was for him to watch his teammates win the World Cup on home soil four years ago.

Injuries have prevented Carter from delivering on the biggest stage on more than one occasion, with a heavy tackle forcing him off in the quarter-final with France in 2007.

A groin problem picked up in the group stage ended his tournament prematurely when New Zealand lifted the title, and he admits that the success left him with mixed feelings.

"That World Cup was really tough for me," the 33-year-old told reporters. "As a team we performed extremely well and to win it was really exceptional, but on a personal level to be knocked out just before the playoff stages with such a serious injury was really tough to take.

"I've had a few injuries throughout my career but that was probably my toughest one, and I was forever asking the whys. Why me? Why now?

"I needed to remain really positive, not only for me to be able to bounce back from such a serious injury like that but also for the team as well. I wanted to help out the guys who moved into my position, and sobbing around the team wasn't going to help anyone."

New Zealand meet Namibia in their second Pool C fixture on Thursday.