The Proteas fell to a six-wicket defeat at the Gabba in a match that only lasted two days to go 1-0 down in the three-match series.
Nortje said the tourists have not been taking things easy in their down time in Brisbane and have been putting in extra training sessions ahead of their trip to Melbourne.
The paceman said: "Luckily we had some facilities in Brisbane and guys have been active, we have not been sitting and chilling at home and doing nothing.
"In the last game probably even a half session the game could have been different, we could have been in a winning position.
"You can't look at losing by six wickets and say it's a big margin on that wicket, it might have been a small margin. We are not really focused on the last game, we are focused on what's going to come up now and try to prepare again.
"Everyone is in a really good space mentally and physically wise. We are just looking forward to starting the game now."
The Proteas' last Test at the iconic MCG was back in 2008 when fast bowler Dale Steyn took 10 wickets and they beat the hosts by nine wickets en-route to a 2-1 series win.
Nortje will be hoping the surface will offer good pace and bounce but not the excessive movement that was seen in the first Test in Brisbane, with the pitch deemed "below average" by the ICC.
When asked what he expects from the conditions in Melbourne, the fast bowler said: "You can't really go into history too much, but it seems like a good wicket in terms of pace and bounce.
"I don't think there will be as much side movement as there was in Brisbane so hopefully we'll just be able to stick to the basics.
"I know it's simple to say but that's what we'll be hoping to do and use our bouncers as a bowling unit. As a bowling unit I don't think there are going to be massive demons in the wicket.
"I've never played here, so I can't speak from experience, but we think it will be a good contest."