The midfielder believes victory against the Red Devils’ neighbours has breathed new life into the squad, and that they can still grab fourth place.
A 1-0 victory at the Etihad Stadium last month revitalised United’s quest to grab fourth place.
With seven games remaining the club lie just one point behind City; and Herrera believes the momentum is with them.
“I think the last game [against City] showed that we are a little bit better than them right now,” the Spaniard said.
“We beat them away in the Manchester derby so we can be optimistic.”
The former Atletic star pointed out that the return of several injured first-teamers would give Louis Van Gaal’s men a boost going into the final straight.
“Man City has a bigger squad – very good players – but I think right now we can fight against them. We are recovering some important players like Ash [Young], Antonio [Valencia], Phil Jones and Shaw,” he said.
“They are going to help us and there is a lot of experience. It’s not going to be easy because City also want to be in the Champions League but I think we are ready to do it [finish in the top four].