McGrath is set to start the return test in the No 1 jersey after his Chicago heroics.
"I actually didn't grab it, some fella handed it to me," McGrath laughed when asked how a pint managed to end up in his hands at full time at Soldier Field.
"Some fella handed it to me and I was glad to have it - I was fairly thirsty after that! It was a Heineken, but everyone in the crowd had two pints in their hand so I just took one."
McGrath is thirsty for a second victory over the No. 1 ranked team in the world and says the Irish are fuelled by proving Chicago was no fluke.
"A lot of things happen once-off," he said. "But if you do it for two in a row, that's when people sit up and listen, and if we want to be taken seriously as an Irish team and as a nation then we have to step up on Saturday and back up what we did in Chicago.
"Probably the monkey is off our back but when you've a win like that you want to win again and, for us as a group, it's an area that we feel really good about, that we can go ahead and go for two from two against that group of players because we've done it before.
"It was a really confidence-boosting thing, especially with the amount of young guys on the team, and you'd have to feel great for the guys who have been there for 10-12 years, plugging away - the likes of Rory (Best) being the first Irish captain to ever captain a winning team against the All Blacks is a huge thing. Personally, I just want more and more of that."
McGrath admitted the Irish know the All Blacks won't be as sloppy was they were in Chicago.
"For us, we showed they're still human, they made mistakes when they were put under pressure," McGrath said.
"Their bread and butter is their silky skills, so this weekend their skills are going to be 10 out of 10.
"For us to go after them and attack them, we can't rest on our laurels and let them attack us. We're at home, we are in front of our families.
"It is going to be an emotional day. It is going to be a special day, not many people get to play the All Blacks two out of three weeks and I think it is a huge task for us. The squad that we have is well able for it."