Attacking prowess
Herrera generally likes to operate in the No.10 role behind the striker, but with Juan Mata and Wayne Rooney already at the Theatre of Dreams the fact he can also play deeper or on the right is a bonus.
United were said to lack creativity in midfield last term and with the Athletic star having a keen eye for key passes and set pieces, he could be the ideal solution to that problem.
Defensively sound
Despite being considered an attacking player, Herrera is no stranger to the defensive side of the game and can be just as useful at the back as going forward.
His tackling is particularly strong and this box-to-box style could suit van Gaal down to the ground.