If the defense is in some sort of quarters or even coverage when number two comes across the formation it can have the effect of taking the safeties' eyes in and he will lose track of number one.
One of the easiest ways to keep things simple in the passing game is through the use of tags. We use tags off of our base plays that allow the players to trade responsibilities. The effect is that the players are learning a new path to their route as opposed to a completely new route. In addition the read for the quarterback changes very little.
One of our most popular tags is the swap tag. This tag will tell the inside receivers that they are going to change their responsibilities. This creates a natural rub which can cause problems for press defenses. It also creates issues for the zone defenses because the player coming into a zone will be coming from a different angle. When a pass defender is locked into a pass route the Swap route can be the tool you need to attack him from a different angle and open up a completion.