Herrera has enjoyed a prolonged run in the starting XI alongside Paul Pogba and Michael Carrick, but the Spain international knows that he will have to work hard to keep his place and have a future at the club.
"Yes, but you never know because if I want to keep playing for United you have to play very well because United is the biggest club in England," he told 'Inside United'
"The club has the capacity to bring any players here so you have to always be at your highest level if you want to keep playing for this club. It's not easy but I hope I can and I will fight for it".
The midfielder also played down the differences between English and Spanish football and insists that it's pretty much the same wherever you go.
"Everyone always asks me that about the differences and to be honest I don't think there is a big difference, football is football everywhere and the good players are good players everywhere," Herrera added.
"Maybe the rhythm of the game here is a little bit higher sometimes. In Spain and other countries they think more about tactics or defending the goal, but here in England everyone wants to attack and that's good for the fans as well".