Wagner acknowledged that his side tailed off in the second half, but said that he was happy with their performance despite falling to a comfortable defeat.
"A disappointing result, not a disappointing performance, especially the first half. I think the players have done everything, left everything on the grass. I have seen passion, desire, the spirit, which we usually have in our game. I felt the energy in the stadium and we were unlucky in the first half," he told reporters.
"We conceded the first goal out of nothing, a deflection goal and then we were unlucky when Steve Mounie only hit the inside of the post. The second goal we conceded shortly before half-time is a goal which we should never concede. In the first line, we defended not like we wanted to defend.
"This was a goal that was easily avoidable because we have spoken about this situation the whole week, how we like to defend, and we have seen we have to be switched on. You can't switch on against a top-quality team like Chelsea. Then we were 2-0 down after I think a good half and I think second half we started very slow, we were shocked.
"This is understandable after this good first half and you sit at half time and you are 2-0 down. Then in the best period which we had in the second half after 20-25 minutes where we hit the bar again, where we were unlucky, we conceded the third one and then at the end it was a deserved win for Chelsea."
The defeat leaves Huddersfield bottom of the Premier League table after the first Saturday of the season.