Kanu's first-half strike looked to have sealed the npower Championship points for Portsmouth until Ibrahima Sonko put into his own goal three minutes from time to level for Forest. Marcus Tudgay fired in the winner deep into stoppage-time to move Davies' side just two points adrift of the Championship play-offs.
Davies said: "Portsmouth are a Premier League club with Premier League players and salaries and it showed with the way they played against us.
"Like ours, their squad is on the small side but they made it very difficult for us. They got their goal and kept hitting us on the counter. They have a physical presence and stature and they are a dangerous side to play against.
"They bullied us in the first half, but we showed great spirit and great determination and it was a wonderful three points to take against an excellent side.
"We had to change our game and the substitutes made an impact to help us turn the game in our favour, it was a great ball from Lewis McGugan and a superb header from Marcus Tudgay that won it after we had got the equaliser."