An All Blacks line-up containing 11 changes are looking for a fifth successive win in this year's tournament against South Africa in Pretoria on Saturday.
After completing back-to-back Tri Nations and Bledisloe Cup wins over Australia, the Kiwis are intent on sealing a clean sweep in the competition.
And Macdonald warned this can only be achieved if the team push themselves individually in their final two games on South African soil.
He told The New Zealand Herald: "Playing for the All Blacks, you are always playing for your career.
"The majority of the guys will be thinking they want to push their chances.
"There's end of the year tour spots up for grabs and the ultimate goal is the World Cup. Every chance you get to impress is a crucial one.
"Very rarely do we get to come over here and play a couple of games in a row, so we're treating it like it's a little series."
Canterbury and Crusaders star Macdonald acknowledged the finale in the Republic will be a tough conclusion to their campaign.
"The All Blacks don't have a great record here and even with the Crusaders we struggle to get two wins," he said.
"It's a difficult country to tour and the Springboks always play with passion at home.
"It's always a bit of a dogfight and you never come out of the game feeling too flash afterwards. It takes a fair bit out of you."