Poor marking allowed Chris Martin and Tomas Kalas to put Fulham 2-0 up and Lucas Piazon was unchallenged as he nodded home Sone Aluko’s cross to make it 3-0.
Martin converted a penalty after a clumsy tackle by Christopher Schindler and Kevin McDonald was also unmarked to wrap up Fulham’s biggest victory since August 2012.
But Wagner was at least relieved that he did not have to go back to the tactical drawing board after a third defeat in four matches left Town still in third place in the Championship table.
“I can leave this game very quickly behind us,” he said. “We don’t have to speak about any tactical problems because we had so many individual mistakes that you couldn’t get anything against any opponent.
“We conceded two early goals after set pieces and we lacked concentration and focus in easy situations.
“We were very sloppy when we had the ball and in the end we totally underperformed today.
“I think Fulham were stronger in every position. We had problems everywhere. We made so many easy mistakes.
“To be fair, it’s easier to analyse. You have to get the small things right to be a competitor and we weren’t a competitor today.
“This happens in football. It shouldn’t but it does and I’ve always said we will have ups and downs on our journey. This was a down.”
Now Wagner must attempt to get the Terriers’ surprise promotion push back on track.
He continued: “We have shown two weeks after we underperformed the first time, against Preston away, that we know what we have to do to get back to our routine – and we played very well against Derby and won.
“Now we have to make sure we confirm what we did and be back to normal next Saturday”
Fulham boss Slavisa Jokanovic was delighted his team had won in front of their own fans for the first time in seven matches.
He said: “We and the supporters deserved that.”
Fulham: Button, Fredericks, Kalas (Ream 81), Sigurdsson, Malone, Johansen, McDonald (Parker 85), Cairney, Aluko (Ayite 75), Piazon, Martin. Unused substitutes: Bettinelli, Odoi, Smith, Sessegnon.
Huddersfield Town: Ward, Smith (Cranie 77), Hudson, Schindler, Lowe (Holmes-Dennis 73), Whitehead (Payne 61), Mooy, Kachunga, Palmer, Bunn, Wells. Unused substitutes: van La Parra, Paurevic, Murphy, Hefele.
Referee: David Coote (Nottinghamshire).