The New Zealand team doctor Deb Robinson will assess MacDonald in Christchurch this week, while there is also a doubt over whether wing Rudi Wulf will make the trip to Cape Town for the match against the Springboks after he suffered a knee sprain playing for North Harbour in the Air New Zealand Cup last Friday.
"We certainly won't be rushing (MacDonald) back to play till he is ready," said Hansen. "We sent him home to be with his family and it's like any head injury it will come right eventually.
"He wasn't that far away but the Doc will see him during the week and we'll make assessments. If he's not right he won't be part of it."
If MacDonald is ruled out the All Blacks coaches will be allowed to call in a specialist replacement from outside the players who have taken part in the Tri-Nations so far.
But Hansen said the other valid option was to use centre Richard Kahui, who played on the wing against Australia, as back-up to Mils Muliaina.
"We're all pretty happy with the way Richard went on Saturday. He's versatile enough to play at full-back. He's played a lot of football there (for the Highlanders in 2006)."
"He certainly handled the challenges (on Saturday) night well. So that's one option. With Rudi struggling with his knee that might be the option but we'll wait and see."