Sportal.co.nz 16.Sep.2012Getty Images
Greyling was carded 17 minutes from the end after he dived into a ruck and appeared to elbow All Blacks captain Richie McCaw.
"It was a cheap shot and it will probably be dealt with accordingly," Hansen said. "The citing commissioner will have a look at it and make a decision."
McCaw shrugged off the incident, in which he was not injured, but he did take a knock to the quad muscle near the end of the game.
The All Blacks have an almost unassailable lead in the championship. They have 16 points with two rounds remaining while South Africa have seven.
"It wasn't a complete performance but it was a torrid test against desperate opposition," Hansen said.
"I was really pleased with the character of our older statesmen and our younger players. We're proud we're unbeaten but we're still looking to improve our game."
Hansen said halfback Aaron Smith had made an emphatic response to his relegation to the reserves after breaking team protocol after the Test in Wellington last week.
Smith scored the game-breaking try with a brilliant snipe midway through the second spell.
"He gave us the response we were looking for. There was really only one response he could deliver and that was to come on and play well. He scored a great try.
"I don't know whether he would be that happy with the try Habana scored for South Africa. He made a difference and that's what we want our run-ons to do. It was a tough week for him but we all make mistakes in our lives."
Hansen thought Dan Carter should be fit to travel to Argentina next week and said the All Blacks would take 28 players for the Tests there and in South Africa.
McCaw said it was a special experience to play in the covered Forsyth Barr Stadium.
"I loved it. It was my first game there. You wouldn't get a better stadium. Yeah, loved it."
McCaw said it was a grueling physical battle.
"They're big men and they put the heat on around the fringes. It was a good old battle and we expected that. It was right up there in terms of intensity.
"Those type of games are fun to play in, especially if you come out on the right side of the scoreline."
McCaw's main concern was the number of kickable penalties conceded by the All Blacks.
The Springboks had eight penalty attempts but succeeded with only two with Morne Steyn (one out of five) having an especially bad night.
Springbok coach Heyneke Meyer said he was disappointed at the outcome.
"We put a lot of pressure on but we could not convert it into points. The All Blacks are a quality side and they didn't panic. We had the opportunities to score and we didn't.
"But we put our bodies on the line and we're looking forward now to the two home Tests. We're improving every week but the scoreboard is the only thing that matters."
Springbok captain Jean de Villiers said his side had to learn from their mistakes and he questioned if the ball had been a factor in his goal-kickers struggling for accuracy.
"We played with an adidas ball and at home we play with a Gilbert. We saw the kickers struggle at this stadium in the World Cup last year.
Neither Meyer nor de Villiers supported the actions of Greyling.
"I'm very big on discipline and I'm very disappointed," Meyer said. "I apologise to Richie."
De Villiers added:" Discipline is non-negotiable."