Ronaldo was red-carded for head-butting Pompey midfielder Richard Hughes, but Redknapp confessed: "I saw a red card flourished and just hoped it wasn't another one for us.
"We will miss Muntari as well. It was two yellow cards, the first an innocuous trip when he chased Ronaldo and later when he went in a bit late. He'll have to watch it in English football."
Redknapp had to do without new skipper Campbell after he damaged a groin muscle in Saturday's 2-2 draw at Derby.
Right-back Lauren injured an ankle in training yesterday and Dejan Stefanovic is also sidelined.
Redknapp said: "It was a fantastic performance. I would have certainly settled for a point tonight before the game.
"Anything you take off United or any of the big four teams has got to be a good result.
"It has always been our trademark. We have a go and that was a typical Portsmouth performance.
"Although United scored in the first half, they didn't make that many chances and David James didn't have to fly about making dozens of saves.
"But I changed it a bit in the second half, pushed Benjani right up front and played two other attacks wide and it worked out.
"United are a great team. They always seem to have five or six different options on the ball and Giggs pops up everywhere.
"But we regularly take points off them here and we were well worth one tonight.
"Benjani scored a great equaliser and the crowd love him for his work-rate and ability. His only failing has been scoring so few goals but he's got two in two games now and hopefully can put that right."