Newcastle United 1 Huddersfield Town 0: Wagner left frustrated by Toon defeat
Wagner, who saw substitute Scott Malone almost level at the death, was disappointed to leave Newcastle empty-handed.
He said: "We are frustrated and a little bit disappointed as well, of course, (to) concede so late in the game in a game where I think, in the second half, our game-plan worked more or less perfectly.
"We wanted to frustrate them, we wanted to play from a deeper block, minimise their chances and hurt them on the counter.
"It was defensively one of our best performances in the second half of the season. The effort, attitude, fighting spirit, togetherness, everything you need when you are in and around the position in the table where we are, was there.
"That's enough for me to get enough confidence for the next games. But you need as well to use your opportunities and we haven't done today, and that's why we conceded this defeat where I think we deserved at least a point for this great defensive attitude and fighting spirit which the players have shown."
Newcastle boss Rafael Benitez praised his players though for their response after fearing they were too relaxed ahead of their Premier League relegation clash with Huddersfield.
The Spaniard had been delighted with the way his squad had trained all week until Friday, when he felt the need to speak out.
His words had the desired effect as Ayoze Perez struck 10 minutes from time to clinch a 1-0 victory at St James' Park which eased the Magpies seven points clear of the relegation zone with seven games remaining.
Benitez said: "This week, we were training really well - apart from yesterday. I was not very happy because they were a little bit relaxed, but during the week, they were training well and you could see the competition between players and you could see that they understand what we have to do as a team.
"We were talking a little bit, but the good thing about this team is they understand and they care, so as soon as we were talking yesterday, but especially today, I knew (from) the way that they were talking between themselves that they were really focused."
Newcastle squandered a series of first-half chances and then saw Mathias Jorgensen go close to the opener for the visitors before Perez struck with his first Premier League goal on Tyneside in two years.
Benitez said: "When the other team is narrow and short, you have to wait, you have to be patient in the right positions and then be sure that when you have a chance, you have to be there.
"He did it and he did it really well."
The Magpies are within touching distance of safety, but their manager is refusing to believe they are already there.
Benitez said: "Forty points is the target, so we have to carry on. We are happy, but carry on."