The team are only avoiding the Premier League relegation zone on goal difference at the moment, and are now on their fourth manager of the campaign.
However, they have reached their first European quarter final in 30 years after beating Midtjylland to advance in the Europa League.
Pereira was full of praise for his team after the game, saying: "I started to do the substitutions not because we are playing in a bad way, because we were playing a fantastic way.
"It was to balance the energy and to be ready for Sunday.
"We proved today that we came here to compete and that we have good, talented players."
Club captain Ryan Yates - who scored his team's second goal in the 2-1 win to give them a chance in extra time and penalties after a 2-2 draw on aggregate - praised the team's sense of unity.
He told TNT Sports: "Considering the changes it just shows the strength in depth we have and the spirit we have.
"At this stage of the season that's what it's all about. It's about showing that togetherness, fighting for each other.
"A lot of lads played today that haven't got many minutes and a lot took their opportunities and will be looking for more minutes for sure."
Meanwhile, former Forest defender Luke Chambers pointed out that the players who were brought in for the game - which the manager making no secret of his focus on the league - will think they've done enough to earn another chance.
Speaking on BBC Radio 5 Live, he said: "The lads that started will be looking at the manager and saying 'we produced the goods tonight, can we get another opportunity at the weekend?'"
Before the game, Pereira - who made nine changes for the game - suggested that avoiding relegation was the priority, rather than European glory.
He told reporters: "It's crucial for the club to keep the position in the Premier League. Today is a chance for a lot of players that are working hard to have a chance."
There is now the added challenge of navigating the additional fixtures that come with last night's win, but the manager is confident.
After the game, he said: "The spirit is different [when we win], the energy is different and the boys deserve it because they are a fantastic group, very good players and with team spirit, character - we showed everything today.
"I don't have any doubt that we have the quality and we will compete to achieve our targets."