Kanu was at the Royal Bafokeng Stadium to see the team work their way past Ethiopia and says the Eagles need all the support from their fans.
"Most average teams are lifted by the support of their fans," he told KickOffNigeria.com. "I know a lot of people have written us off already, but this team will surprise people.
"I remember the same thing happened at the Nations Cup in 2004 when we were about to face Cameroon, but we ended up beating them 2-1. I believe in this team and the coach."
Kanu said the fans would have to do their part and not send negative energy to the team.
"The boys need encouragement, and if they see that the fans are backing them to win, they will give more than their usual.
"But if we keep talking about how they will lose, how can the players raise their game when their own fans expect them to lose.
"Even if every other person says they will lose, let us as Nigerians believe in them."