Carson was drafted in on loan from Bury last week following John Sullivan's error-strewn display in the 4-2 defeat at York.
And the 25-year-old made his mark with a fine late double save to keep a first league clean sheet for Pompey in seven matches.
Whittingham said: "Keepers have to keep their concentration and he did that.
"He's put in a steady performance and then made two great saves at the death."
- Sports & Recreation