The Spaniard, signed in 2014, endured two murky seasons under Louis van Gaal, displaying moments of brilliance but ultimately failing to discover an identity at Old Trafford.
And Herrera was quick to thank the Portuguese for overseeing such a fruitful period in his career.
“Our manager is helping me a lot but I have done it by myself as well,” he said. “My first two seasons here I played 71 games so it’s not a bad number of games.
“But, of course, I cannot lie. This is the time I am enjoying most at Man United. But since the first day I came I’ve felt very lucky because I play for this club.
“I think all of you have seen that since the beginning of the season in a few games my role changes.
“He has helped me a lot to get the knowledge about that role.”
The 27-year-old’s evolution at Old Trafford has been explosive. He has, over the past few months, gone from being a useful asset to simply fundamental, furiously asserting himself every week in midfield.
A huge change, yes, but one brought about through relatively simple means: Mourinho arrived in June and, having watched Herrera closely over the past year or so, made it clear to the Spaniard what his role was, and he hasn’t looked back since.