The Toon won 2-0 thanks to goals from Bruno Guimaraes and Malick Thiaw.
Glasner said afterwards: "A disappointing defeat, disappointing result.
“The most disappointing part for me is conceding another two goals from set-plays – five of our last six defeats, we just conceded goals from set-plays, and then you can’t win games. This is what we have to get sorted.
“It's my responsibility, together with my staff, to give the players better solutions, that they feel more comfortable and can defend this in a better way.
“It's always a second phase where we are not really structured and then conceding goals, because there's many parts of the game I was really pleased today. I think we played really well. (Apart from) maybe the last five or six, seven minutes, when we went all in to get our goal – before that, we didn't give them chances from open play. We defended really well."
On Brennan Johnson's debut after his arrival from Tottenham, Glasner added, “I was pleased with his debut. He showed what he would bring to the team.
“Of course, I could see in a few situations that his understanding with his teammates was not here after one day of training, when he's trained with half of the group, but he will definitely help us in the games.
“I was pleased with his debut and performance today.”