The Rams hit back from conceding a first-minute goal to score three before the midway point of the opening half, and the former England boss has described the result as a "big win".
The 52-year-old is quoted by BBC Sport as saying: "There was a real focus and determination and it was a big win. Psychologically, it was huge. Performance is the key thing and that was excellent.
"We've got one foot in the door in terms of the playoffs and Saturday at home to Huddersfield becomes another big game. We need to get over the line."
Derby have overtaken Queens Park Rangers to move up to third position in the Championship table, but they remain 11 points adrift of second-placed Burnley.