Carson was caught out of position for the opener and belted an intended clearance against Nigel Reo-Coker for a comical own goal, O'Neill refused to condemn the man on loan from Anfield.
"The second goal was a fluke," said the Villa manager. "You will have to watch a lot of games before you'll see a goal like that again. Overall I've been pleased with Scott Carson."
Portsmouth boss Harry Redknapp, delighted at the end of a week which brought three wins, saw Pompey emerge as FA Cup favourites and climb above Villa into sixth place in the Premier League, was also generous to the keeper.
He said: "Carson's had a terrific season with Villa. The goal was one of those things."