The All Blacks have already lost star fly-half Dan Carter to a tournament-ending groin injury and McCaw has been struggling with a foot injury.
But, after pulling out of two pool matches, McCaw today insisted he would be "good to go" against the Pumas at Eden Park.
"The foot feels good after a bit of rest last week and over the weekend," said McCaw.
"I trained with the team yesterday and it is always hard when you have missed training here and there.
"I would like to think that, when you have been playing this game for a few years, you know what you need to do to get in form.
"I've just got to make sure I get into form and that's the key. I am confident and all the boys are in pretty good shape.
"The boys are excited. I suppose there are a few nerves because we are at the business end, but there are lots of excitement, too. The boys can't wait to get stuck into it."
McCaw became New Zealand's first Test centurion in the opening game of the World Cup against France and he will be joined in that exclusive club tomorrow by Mils Muliaina.
"It would be great to see him out there for the milestone. He is a bit of a champion," McCaw said.
"He's been with the All Blacks for a long time and you would agree that every single time he is out in the field, he's contributed in a huge way.
"He just wants to do the job and not feel any different. I guess, from our point of view, we make it a memorable night for him."
Ma'a Nonu, Cory Jane and Piri Weepu return to the All Blacks' side, with Sonny Bill Williams moving to the wing while McCaw is joined up front by hooker Keven Mealamu and lock Brad Thorn.
The bookies have given New Zealand a 27-point start against the injury-hit Pumas, who have recalled Exeter wing Gonzalo Camacho, full-back Martin Rodriguez, lock Manuel Carizza and veteran prop Rodrigo Roncero.
"We draw strength and being the underdog puts us in a stronger position. It is a position we are comfortable with," said Camacho.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
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Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
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The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.