Foul Play on Diggersby isn't actually as stupid as it sounds; Foul Play's mechanics factor in the user's Huge Power (or Pure Power) and apply it to the opponent's Attack stat, meaning that when Huge Power Diggersby uses Foul Play its damage output is doubled. Because of this, I'd actually see Diggersby being a decent stallmon if it could run Huge Power and Cheek Pouch at the same time.