As a former amateur keeper at Mickey Mouse level, all I can say is that any deflection is often fatal for a goalkeeper. That's because an element of goalkeeping involves using muscle memory to anticipate the likely trajectory of a shot. If a player uses his right foot and is in a certain situation, the goalkeeper's mind is already subconsciously cycling through 1,000 memories of this almost exact situation. He will then anticipate the likely trajectory of the shot and make his move - often in advance - as close to the moment the player makes contact with the ball as possible. Pickford probably had the Cavani shot covered - but the Uruguayan got lucky with the deflection. Or if you are really critical, you could argue that our defender got caught between making a clean block and just getting out of the bloody way. Worst of both worlds for the keeper and a prime example of those moments when it would be better for him if the defender was slightly late with his contact.