"Everyone, myself included, put a lot of effort into the trip to South Africa. We took a while to get into that game and at the end we did what we needed to do," McCaw told stuff.co.nz.
"Then we got to Melbourne and I don't think we were all mentally quite there. We thought we were but come the end of it we weren't.
"The frustrating part was we got the foundation right, we just didn't finish the job.
"And myself, and the other leaders in the team, needed to make sure when the Wallabies got their tails up we changed our tack a wee bit - perhaps we didn't need to play with the ball behind the gain-line as we did a bit.
"I definitely take some of the responsibility for that. It has been a big learning curve for everyone."
McCaw again leads the Kiwis at Jade Stadium, with a win vital to their chances of retaining the trophy.