The two sides played out an eventful draw with goals coming from Neco Williams and then Julio Enciso in the first half.
The biggest talking point wasn’t the goals or result; however, it was when Issa Diop brought James McAtee down when the Forest ace looked to be through on goal.
Initially referee Thomas Bramall waved it away without even awarding a free kick, but VAR took a look to see if Diop had in fact denied an obvious goalscoring opportunity.
Bramall was called over to the monitor to take a look, but instead of brandishing a red card as many had expected, he showed a yellow.
Speaking to Sky Sports after the game, Glasner was clearly unhappy with the decision.
"Mixed feelings. More positive, playing so well and we had a great start and after 15-20 minutes we were the better side and started to control the game," he said.
“Then we made the mistake and it's 1-1. The momentum can change but the reaction second half was amazing. We had many situations where we could score.
“I loved the reaction, the way we played and the spirit. We are moving up on performances and staying patient."
On not putting chances away: "We don't need to address it. Sometimes you try a huge effort and things don't work. You are encouraging them to keep going because you have these periods in sport and life.
“When I see the way we play, the spirit and the chances, the only way now is to stay patient and not make the problem bigger. It's a question of time and maybe in a few weeks you will be asking why we are scoring so many goals."
Was it a red card? "Yes, I felt during the game it was a clear red card. I think he (McAtee) was preparing his finish by going a bit right. I think it was the wrong decison but we couldn't have played a more dominant second half.
“We created enough chances to decide the game and that's why I will never blame the referee. Many decisions not on our side this season but again, we stay patient and keep going.
"Referee's decison is always subjective. I liked that he went to the screen, this is the right procedure.
“It was wrong (decision) but he didn't do it on purpose and I have to be honest - I remember the situation at Palace in the FA Cup final when Dean Henderson touched the ball outside the box and it was the same explanation and he didn't get a red card but today I feel it was wrong."