I don't agree that he is only about commitment and energy. I think he has real quality to his game. His close control and inter-play in tight spaces are very good. His passing in-between lines is also good, but his long range passing is below par. His first touch is decent, and he can dribble past opponents to gain momentum. He has quick feet, but his top speed is arguably lower than Mata's - the guy just cannot sprint. He is good defensively, and leads by example.
He may not be as tall as Matic, but on pretty much any other account he is better suited playing next to Pogba. I would love to see a midfield of Herrera behind Fred and Pogba. I think that is a midfield with the potential of being one of the best in the league. Quick feet, passing, vision, dribbling, strength pressing all combined. Pogba has, by far, the best passing range at the club, Fred is very quick for a central midfielder and can go past people, as can Pogba, and Herrera is very good at cutting out supply lines from the opposition. Please bench Matic!