He advertises which way it's going. But if a penalty taker just wellies the ball, kinetic energy takes over, nullifying the advertising*. It's the little uncertain shuffle-footing before striking that balls' things up, because it compromises velocity.
*if a grain of sand hits earth at velocity 99% speed of light, the amount of kinetic energy such an object has is given by
KE = mc²(1/√(1−β²) − 1)
where:
m = the object's mass (in this example, about 0.000011 kg)
c = speed of light (about 3×10^8 meters/sec)
β = object's speed as a fraction of c (in this example, 0.9999)
Plugging in the numbers, we get
K.E.= 4.94 × 10^15 J
That's about 5600 times the energy released in the Hiroshima bomb.
i.e. It would penetrate the earth and emerge out the other side in milliseconds
No goal keeper is stopping that.