The midfielder revealed every member of the squad is high on confidence – and that Jose Mourinho should take great credit for that.
"We are very, very comfortable with this manager," Herrera told manutd.com. "Every training session we are enjoying. I feel very good when I have played. I feel his confidence every day and I think all my team-mates are the same.
"He is very close with us so you feel important, you feel part of this. That's the most important thing – when you feel part of something and he is showing to all of us that he's going to give time to everyone.
"If you want to make a good season, if you want to win trophies, you cannot do it with 12, 13 players. Everyone is going to be important and everyone is going to get his moment. We have a good squad and we play with freedom because we feel the confidence of our manager."