Herrera joins on-loan from City after spending last season with New York City FC.
He said, "It's a dream for me, to reach Europe in the best league in the world, I come to a humble and struggling team, I want to improve things and save the team, I'm a midfield player that supports in attack and in defence.
"I become strong in the 50-50 balls.
"The month of December I was training under Pep.
"I was very excited to be able to work with a great team like Manchester."