The defending champions beat Argentina 26-16 and Namibia 58-14 in their first two games but failed to produce their usual slick ruthless rugby and they are keen to put that right against Georgia on Friday.
"Performance-wise, we need to take a step up," McCaw told reporters.
"We have all had a run in the first two games so there are no excuses for not being ready to go."
Coach Steve Hansen has rotated the squad to keep his players fresh.
"When you haven't played for a while there is always a bit if rustiness," McCaw said.
"You don't like to use it as an excuse but I think that was what let us down last week against Namibia. The guys were trying hard but were making some crucial mistakes. You can't afford to let that happen."
The All Blacks are facing Georgia for the first time.
"I don't think you need to be playing against a new side like Georgia to keep you fresh," McCaw said.
"The fact that we are going into the third game of the World Cup means there is a bit of an edge there, regardless of who the opposition is.
"We understand who we are up against but the main focus is about us getting our game spot on. The excitement we have got from that is enough. Still, playing against a side like Namibia or Georgia is something different and add to that the Millennium Stadium and it's pretty exciting."
Assistant coach Ian Foster scoffed at the suggestion that New Zealand's modest performances had kept the world champions out of the tournament spotlight.
"Maybe from the outside looking in it appears as though we are going under the radar," he said.
"However, from our point of view that's not the case. We are focusing on us and what we need to do and we need to show some improvements because at the end of next week we are at the business end of the competition," Foster added.
"That's when nobody is under the radar. There has certainly been a real edge at training this week."
(editing by Justin Palmer)
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