Forest boss Billy Davies saw his much changed side relinquish a 1-0 lead and pointed to three incidents in the game that he thought were key.
He said: "I thought we played some very good football in the first half. It was just a disappointment that we conceded the goal before half time because that was a big blow to us.
"We should have then taken the lead at 1-1 but Matt Derbyshire was unfortunate to miss his chance. Then they break up the other end, get quite a soft free kick and take the lead, but that's what happens in cup football and you have to be clinical."
He added: "It was nice to get some minutes into the legs of some of the squad players tonight. Tonight was a big lesson for the team but there were some very good performances out there.
"Ultimately we came here with a strong team to win th game but unfortunately we couldn't do that. It all boiled down to those key moments but we'll learn and move on."
Sean Dyche was once again full of praise for his strike pair and in particular Danny Ings who, for the second time in a week, scored two goals in a game at Turf Moor.
"We had a lot of belief in Danny last year, but he was a young man learning his trade," said Dyche. "But we felt there were good things to come from him this season and we knew he would benefit from pre-season.
"It's not just his goals though. The thing I am admiring is his will and desire for the team. It's nothing short of fantastic.
"He is a joy to work with and his goals were fabulous tonight. There are so many good things here at the minute though and I don't want to take anything away from Danny, who was fantastic again tonight, but behind him, the team's mentality and what they are giving the fans and the people of Burnley is an important factor.
"We offered to the group the small squad and everyone being in it together and they have bought into that. They also know they can't let each other down because we are so tight knit."
He continued: "Tonight was the first time we've come from being behind this season. We usually start well in games and we didn't tonight if I'm honest. We looked off the pace and didn't pass or move the ball very well, but we want that mentality that we are never beaten and the lads are really grasping that.
"There were four changes and that's quite a lot in our side. Sometimes that can affect it as people find their feet, but it took their goal to bring us back to life.
"After that Ingsy showed a couple of moments of real class to set things up and then the lads slowly but surely got back to what they have been doing.
"In the second half we got on the front foot more and some of our counter attacking was a joy to watch, mixed with good energy and a solid framework. The lads are going well at the moment and we are enjoying it, but nobody here is getting carried away."