Benjani and Hermann Hreidarsson's deflected strikes early in the second half did the damage as Pompey moved up to fifth.
Redknapp saluted goal hero Benjani who followed up last week's hat-trick against Reading with the vital opening strike as Pompey secured a fourth successive win in all competitions.
Redknapp said: "Benji is a very good player, always has been. The season we made a great escape from relegation he was superb with his work rate and the fans idolised him even though he scored only a very few goals.
"Kanu has done really well for us, too, but he's going to have to try and get his place back now after injury.
"We're on a good little run and it's been a fantastic start to the season. We have just got to keep going.
"It was not our best performance today in the first half but I just said to the players 'keep passing that ball, keep getting it to Sean Davis who is the spare man in midfield'.
"And they did it well after that. Of course it is possible we will challenge for Europe again this season but so will Newcastle, West Ham and many others.
"I'm not getting too carried away. Last week the 7-4 against Reading was a bit weird. A one-off probably but it's another good result today and I'm still happy to think we might finish in the top half of the table."