Implementing spell casts in entity component systems ?

I want to implement an entity component system, but I've been some trouble as of late. Let's say that I have a fire ball spell that spawns a ball of fire which moves towards a random enemy in 500 units range. In an OO architecture, I would have a Player class and I could simply detect a keypress and cast the spell like so:

function player:update(dt)
  if is_key_pressed('e') then
     self:cast_fire_ball()
  end
end

and the cast fireball spell implementation would be something close to this:

function Player:cast_fire_ball()
    -- query the world for nearby units, filter …