Watching over the weekend the player that Salah reminded me of most was Romario. Romario had this brilliant way of waiting until the last second minute so that a defender/keeper had to make a decision, and thats when he had them right where he wanted them.
Doing nothing is remarkably difficult when opponents are surrounding you or charging towards you, it takes an unnatural level of calm. If you can wait for your opponent to make the first move you have something to exploit, a mistake,a gap, an over commitment. It only works if the opponents are so terrified they feel that they must do something to prevent the inevitable. Salah instilled that level of feat in Watford. Look at the 3rd goal he scored at the weekend, thats what terrified defenders do.