Midfielder Herrera won the hearts of the Old Trafford fans with his ferocious efforts in the centre of the park this season.
The Spaniard only played a bit-part role under Louis van Gaal the previous season but Mourinho told Herrera straight away that he wanted him in his plans.
Herrera has revealed that he had a meeting with Mourinho before the start of the season.
He was told that he would be “important” to the team if he improved on some aspects of his game – and was prepared to play in some different roles.
“I know it is difficult to play in a big club like Manchester United as a No.10 because you know how many goals you have to score to play there,” Herrera told Sky Sports.
“So I thought I had to add something to my game. I had to give more options to the manager. We both agreed.
“He told me that I was going to play sometimes a different role in the team. He told me sometimes I was going to play more defensive and in other games he was going to need me more forward. I told him I’d play wherever he wanted me to play and I would give my best.”
Herrera’s future at United has come under question in recent weeks with him linked with moves back to Spain with Barcelona and Valencia.
New Barca boss Ernesto Valverde managed Herrera during his time at Athletic Bilbao but the 27-year-old is set to turn down a reunion.
Valencia have been linked with a £30million swoop.